diff --git a/generator/internal/language/rust.go b/generator/internal/language/rust.go
index f658a815d..8a8b7fe33 100644
--- a/generator/internal/language/rust.go
+++ b/generator/internal/language/rust.go
@@ -540,9 +540,9 @@ func rustAddQueryParameter(f *api.Field) string {
 		// few requests use nested objects as query parameters. Furthermore,
 		// the conversion is skipped if the object field is `None`.`
 		if f.Optional || f.Repeated {
-			return fmt.Sprintf(`let builder = req.%s.iter().try_fold(builder, |builder, p| { use gax::query_parameter::QueryParameter; serde_json::to_value(p).map_err(Error::serde)?.add(builder, "%s").map_err(Error::other) })?;`, rustToSnake(f.Name), f.JSONName)
+			return fmt.Sprintf(`let builder = req.%s.as_ref().map(|p| serde_json::to_value(p).map_err(Error::serde) ).transpose()?.into_iter().fold(builder, |builder, v| { use gax::query_parameter::QueryParameter; v.add(builder, "%s") });`, rustToSnake(f.Name), f.JSONName)
 		}
-		return fmt.Sprintf(`let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.%s).map_err(Error::serde)?.add(builder, "%s").map_err(Error::other)? };`, rustToSnake(f.Name), f.JSONName)
+		return fmt.Sprintf(`let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.%s).map_err(Error::serde)?.add(builder, "%s") };`, rustToSnake(f.Name), f.JSONName)
 	default:
 		if f.Optional || f.Repeated {
 			return fmt.Sprintf(`let builder = req.%s.iter().fold(builder, |builder, p| builder.query(&[("%s", p)]));`, rustToSnake(f.Name), f.JSONName)
diff --git a/generator/internal/language/rust_test.go b/generator/internal/language/rust_test.go
index ea2bdcb94..f777c91d2 100644
--- a/generator/internal/language/rust_test.go
+++ b/generator/internal/language/rust_test.go
@@ -1121,15 +1121,15 @@ func TestRust_AsQueryParameter(t *testing.T) {
 		field *api.Field
 		want  string
 	}{
-		{optionsField, `let builder = req.options_field.iter().try_fold(builder, |builder, p| { use gax::query_parameter::QueryParameter; serde_json::to_value(p).map_err(Error::serde)?.add(builder, "optionsField").map_err(Error::other) })?;`},
+		{optionsField, `let builder = req.options_field.as_ref().map(|p| serde_json::to_value(p).map_err(Error::serde) ).transpose()?.into_iter().fold(builder, |builder, v| { use gax::query_parameter::QueryParameter; v.add(builder, "optionsField") });`},
 		{requiredField, `let builder = builder.query(&[("requiredField", &req.required_field)]);`},
 		{optionalField, `let builder = req.optional_field.iter().fold(builder, |builder, p| builder.query(&[("optionalField", p)]));`},
 		{repeatedField, `let builder = req.repeated_field.iter().fold(builder, |builder, p| builder.query(&[("repeatedField", p)]));`},
 		{requiredEnumField, `let builder = builder.query(&[("requiredEnumField", &req.required_enum_field.value())]);`},
 		{optionalEnumField, `let builder = req.optional_enum_field.iter().fold(builder, |builder, p| builder.query(&[("optionalEnumField", p.value())]));`},
 		{repeatedEnumField, `let builder = req.repeated_enum_field.iter().fold(builder, |builder, p| builder.query(&[("repeatedEnumField", p.value())]));`},
-		{requiredFieldMaskField, `let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.required_field_mask).map_err(Error::serde)?.add(builder, "requiredFieldMask").map_err(Error::other)? };`},
-		{optionalFieldMaskField, `let builder = req.optional_field_mask.iter().try_fold(builder, |builder, p| { use gax::query_parameter::QueryParameter; serde_json::to_value(p).map_err(Error::serde)?.add(builder, "optionalFieldMask").map_err(Error::other) })?;`},
+		{requiredFieldMaskField, `let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.required_field_mask).map_err(Error::serde)?.add(builder, "requiredFieldMask") };`},
+		{optionalFieldMaskField, `let builder = req.optional_field_mask.as_ref().map(|p| serde_json::to_value(p).map_err(Error::serde) ).transpose()?.into_iter().fold(builder, |builder, v| { use gax::query_parameter::QueryParameter; v.add(builder, "optionalFieldMask") });`},
 	} {
 		got := rustAddQueryParameter(test.field)
 		if test.want != got {
diff --git a/generator/testdata/rust/openapi/golden/src/transport.rs b/generator/testdata/rust/openapi/golden/src/transport.rs
index ad3390d7a..6144dd676 100755
--- a/generator/testdata/rust/openapi/golden/src/transport.rs
+++ b/generator/testdata/rust/openapi/golden/src/transport.rs
@@ -263,7 +263,7 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             ))
             .query(&[("alt", "json")])
             .header("x-goog-api-client", reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER));
-        let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.update_mask).map_err(Error::serde)?.add(builder, "updateMask").map_err(Error::other)? };
+        let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.update_mask).map_err(Error::serde)?.add(builder, "updateMask") };
         self.inner.execute(
             builder,
             Some(req.request_body),
@@ -328,7 +328,7 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             ))
             .query(&[("alt", "json")])
             .header("x-goog-api-client", reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER));
-        let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.update_mask).map_err(Error::serde)?.add(builder, "updateMask").map_err(Error::other)? };
+        let builder = { use gax::query_parameter::QueryParameter; serde_json::to_value(&req.update_mask).map_err(Error::serde)?.add(builder, "updateMask") };
         self.inner.execute(
             builder,
             Some(req.request_body),
diff --git a/generator/testdata/rust/protobuf/golden/secretmanager/src/transport.rs b/generator/testdata/rust/protobuf/golden/secretmanager/src/transport.rs
index 39e942c83..72dcf19f4 100755
--- a/generator/testdata/rust/protobuf/golden/secretmanager/src/transport.rs
+++ b/generator/testdata/rust/protobuf/golden/secretmanager/src/transport.rs
@@ -132,7 +132,7 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             ))
             .query(&[("alt", "json")])
             .header("x-goog-api-client", reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER));
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| { use gax::query_parameter::QueryParameter; serde_json::to_value(p).map_err(Error::serde)?.add(builder, "updateMask").map_err(Error::other) })?;
+        let builder = req.update_mask.as_ref().map(|p| serde_json::to_value(p).map_err(Error::serde) ).transpose()?.into_iter().fold(builder, |builder, v| { use gax::query_parameter::QueryParameter; v.add(builder, "updateMask") });
         self.inner.execute(
             builder,
             Some(req.secret),
@@ -308,7 +308,7 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             ))
             .query(&[("alt", "json")])
             .header("x-goog-api-client", reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER));
-        let builder = req.options.iter().try_fold(builder, |builder, p| { use gax::query_parameter::QueryParameter; serde_json::to_value(p).map_err(Error::serde)?.add(builder, "options").map_err(Error::other) })?;
+        let builder = req.options.as_ref().map(|p| serde_json::to_value(p).map_err(Error::serde) ).transpose()?.into_iter().fold(builder, |builder, v| { use gax::query_parameter::QueryParameter; v.add(builder, "options") });
         self.inner.execute(
             builder,
             None::<gax::http_client::NoBody>,
diff --git a/src/gax/src/query_parameter.rs b/src/gax/src/query_parameter.rs
index 063fd3d06..13d11404d 100644
--- a/src/gax/src/query_parameter.rs
+++ b/src/gax/src/query_parameter.rs
@@ -29,29 +29,21 @@
 //! public because we will generate many crates (roughly one per service), and
 //! most of these crates will use these helpers.
 
-type Result<T> = std::result::Result<T, crate::request_parameter::Error>;
-
 /// [QueryParameter] is a trait representing types that can be used as a query
 /// parameter.
 pub trait QueryParameter {
-    // TODO(#610) - remove the add() method.
-    fn add(&self, builder: reqwest::RequestBuilder, name: &str) -> Result<reqwest::RequestBuilder>;
-    fn append(&self, builder: reqwest::RequestBuilder, name: &str) -> reqwest::RequestBuilder;
+    fn add(self, builder: reqwest::RequestBuilder, name: &str) -> reqwest::RequestBuilder;
 }
 
 impl QueryParameter for serde_json::Value {
-    fn add(&self, builder: reqwest::RequestBuilder, name: &str) -> Result<reqwest::RequestBuilder> {
-        Ok(self.append(builder, name))
-    }
-
-    fn append(&self, builder: reqwest::RequestBuilder, name: &str) -> reqwest::RequestBuilder {
-        match &self {
-            Self::Object(object) => object.iter().fold(builder, |builder, (k, v)| {
-                v.append(builder, format!("{name}.{k}").as_str())
+    fn add(self, builder: reqwest::RequestBuilder, name: &str) -> reqwest::RequestBuilder {
+        match self {
+            Self::Object(object) => object.into_iter().fold(builder, |builder, (k, v)| {
+                v.add(builder, format!("{name}.{k}").as_str())
             }),
             Self::Array(array) => array
-                .iter()
-                .fold(builder, |builder, v| v.append(builder, name)),
+                .into_iter()
+                .fold(builder, |builder, v| v.add(builder, name)),
             Self::Null => builder,
             Self::String(s) => builder.query(&[(name, s)]),
             Self::Number(n) => builder.query(&[(name, format!("{n}"))]),
@@ -93,7 +85,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(
             split_query(&request),
@@ -118,7 +110,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(
             split_query(&request),
@@ -133,7 +125,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(split_query(&request), Vec::<&str>::new());
         Ok(())
@@ -145,7 +137,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(split_query(&request), vec!["name=abc123"]);
         Ok(())
@@ -157,7 +149,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(split_query(&request), vec!["name=7.5"]);
         Ok(())
@@ -169,7 +161,7 @@ mod tests {
         let builder = reqwest::Client::builder()
             .build()?
             .get("https://test.googleapis.com/v1/unused");
-        let builder = value.add(builder, "name")?;
+        let builder = value.add(builder, "name");
         let request = builder.build()?;
         assert_eq!(split_query(&request), vec!["name=true"]);
         Ok(())
diff --git a/src/gax/src/request_parameter.rs b/src/gax/src/request_parameter.rs
index 690523dec..da88b3ec7 100644
--- a/src/gax/src/request_parameter.rs
+++ b/src/gax/src/request_parameter.rs
@@ -14,12 +14,6 @@
 
 pub(crate) trait RequestParameter {}
 
-#[derive(thiserror::Error, Debug)]
-pub enum Error {
-    #[error("cannot format as request parameter {0:?}")]
-    Format(Box<dyn std::error::Error + Send + Sync>),
-}
-
 impl RequestParameter for i32 {}
 impl RequestParameter for i64 {}
 impl RequestParameter for u32 {}
diff --git a/src/gax/tests/query_parameters.rs b/src/gax/tests/query_parameters.rs
index 08f17aeae..690cafcb1 100644
--- a/src/gax/tests/query_parameters.rs
+++ b/src/gax/tests/query_parameters.rs
@@ -118,6 +118,7 @@ mod test {
 
     // A new version of the generator will generate code as follows for query parameters.
     fn add_query_parameters(request: &FakeRequest) -> Result<reqwest::RequestBuilder> {
+        use gax::error::Error;
         let client = reqwest::Client::builder().build()?;
         let builder = client.get("https://test.googleapis.com/v1/unused");
 
@@ -164,52 +165,53 @@ mod test {
                 builder.query(&[("repeatedEnumValue", &p.value())])
             });
 
-        let builder = request.duration.iter().try_fold(builder, |builder, p| {
-            use gax::error::Error;
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(&p)
-                .map_err(Error::serde)?
-                .add(builder, "optionalDuration")
-                .map_err(Error::other)
-        })?;
-
-        let builder = request.field_mask.iter().try_fold(builder, |builder, p| {
-            use gax::error::Error;
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(&p)
-                .map_err(Error::serde)?
-                .add(builder, "fieldMask")
-                .map_err(Error::other)
-        })?;
+        let builder = request
+            .duration
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "optionalDuration")
+            });
+        let builder = request
+            .field_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "fieldMask")
+            });
         let builder = {
-            use gax::error::Error;
             use gax::query_parameter::QueryParameter;
             serde_json::to_value(&request.required_field_mask)
                 .map_err(Error::serde)?
                 .add(builder, "requiredFieldMask")
-                .map_err(Error::other)?
         };
 
-        let builder = request.timestamp.iter().try_fold(builder, |builder, p| {
-            use gax::error::Error;
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(&p)
-                .map_err(Error::serde)?
-                .add(builder, "expiration")
-                .map_err(Error::other)
-        })?;
-
+        let builder = request
+            .timestamp
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "expiration")
+            });
         let builder = request
             .optional_nested
-            .iter()
-            .try_fold(builder, |builder, p| {
-                use gax::error::Error;
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
                 use gax::query_parameter::QueryParameter;
-                serde_json::to_value(&p)
-                    .map_err(Error::serde)?
-                    .add(builder, "optionalNested")
-                    .map_err(Error::other)
-            })?;
+                v.add(builder, "optionalNested")
+            });
 
         Ok(builder)
     }
diff --git a/src/generated/cloud/secretmanager/v1/src/transport.rs b/src/generated/cloud/secretmanager/v1/src/transport.rs
index 2eb97fc7e..a60c628bc 100755
--- a/src/generated/cloud/secretmanager/v1/src/transport.rs
+++ b/src/generated/cloud/secretmanager/v1/src/transport.rs
@@ -141,13 +141,16 @@ impl crate::traits::SecretManagerService for SecretManagerService {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "updateMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .update_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "updateMask")
+            });
         self.inner.execute(builder, Some(req.secret), options).await
     }
 
@@ -319,13 +322,16 @@ impl crate::traits::SecretManagerService for SecretManagerService {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.options.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "options")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .options
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "options")
+            });
         self.inner
             .execute(builder, None::<gax::http_client::NoBody>, options)
             .await
diff --git a/src/generated/cloud/workflows/v1/src/transport.rs b/src/generated/cloud/workflows/v1/src/transport.rs
index 3e4533ef5..4fa5066d3 100755
--- a/src/generated/cloud/workflows/v1/src/transport.rs
+++ b/src/generated/cloud/workflows/v1/src/transport.rs
@@ -150,13 +150,16 @@ impl crate::traits::Workflows for Workflows {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "updateMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .update_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "updateMask")
+            });
         self.inner
             .execute(builder, Some(req.workflow), options)
             .await
diff --git a/src/generated/openapi-validation/src/transport.rs b/src/generated/openapi-validation/src/transport.rs
index 7838e7a26..66b03b884 100755
--- a/src/generated/openapi-validation/src/transport.rs
+++ b/src/generated/openapi-validation/src/transport.rs
@@ -332,7 +332,6 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             serde_json::to_value(&req.update_mask)
                 .map_err(Error::serde)?
                 .add(builder, "updateMask")
-                .map_err(Error::other)?
         };
         self.inner
             .execute(builder, Some(req.request_body), options)
@@ -418,7 +417,6 @@ impl crate::traits::SecretManagerService for SecretManagerService {
             serde_json::to_value(&req.update_mask)
                 .map_err(Error::serde)?
                 .add(builder, "updateMask")
-                .map_err(Error::other)?
         };
         self.inner
             .execute(builder, Some(req.request_body), options)
diff --git a/src/generated/spanner/admin/database/v1/src/transport.rs b/src/generated/spanner/admin/database/v1/src/transport.rs
index 3e0080799..9478658df 100755
--- a/src/generated/spanner/admin/database/v1/src/transport.rs
+++ b/src/generated/spanner/admin/database/v1/src/transport.rs
@@ -125,13 +125,16 @@ impl crate::traits::DatabaseAdmin for DatabaseAdmin {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "updateMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .update_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "updateMask")
+            });
         self.inner
             .execute(builder, Some(req.database), options)
             .await
@@ -269,14 +272,14 @@ impl crate::traits::DatabaseAdmin for DatabaseAdmin {
         let builder = builder.query(&[("backupId", &req.backup_id)]);
         let builder = req
             .encryption_config
-            .iter()
-            .try_fold(builder, |builder, p| {
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
                 use gax::query_parameter::QueryParameter;
-                serde_json::to_value(p)
-                    .map_err(Error::serde)?
-                    .add(builder, "encryptionConfig")
-                    .map_err(Error::other)
-            })?;
+                v.add(builder, "encryptionConfig")
+            });
         self.inner.execute(builder, Some(req.backup), options).await
     }
 
@@ -341,13 +344,16 @@ impl crate::traits::DatabaseAdmin for DatabaseAdmin {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "updateMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .update_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "updateMask")
+            });
         self.inner.execute(builder, Some(req.backup), options).await
     }
 
@@ -553,13 +559,16 @@ impl crate::traits::DatabaseAdmin for DatabaseAdmin {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.update_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "updateMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .update_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "updateMask")
+            });
         self.inner
             .execute(builder, Some(req.backup_schedule), options)
             .await
diff --git a/src/generated/spanner/admin/instance/v1/src/transport.rs b/src/generated/spanner/admin/instance/v1/src/transport.rs
index d12f4713a..ca7525a22 100755
--- a/src/generated/spanner/admin/instance/v1/src/transport.rs
+++ b/src/generated/spanner/admin/instance/v1/src/transport.rs
@@ -199,14 +199,14 @@ impl crate::traits::InstanceAdmin for InstanceAdmin {
         let builder = builder.query(&[("filter", &req.filter)]);
         let builder = req
             .instance_deadline
-            .iter()
-            .try_fold(builder, |builder, p| {
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
                 use gax::query_parameter::QueryParameter;
-                serde_json::to_value(p)
-                    .map_err(Error::serde)?
-                    .add(builder, "instanceDeadline")
-                    .map_err(Error::other)
-            })?;
+                v.add(builder, "instanceDeadline")
+            });
         self.inner
             .execute(builder, None::<gax::http_client::NoBody>, options)
             .await
@@ -233,14 +233,14 @@ impl crate::traits::InstanceAdmin for InstanceAdmin {
         let builder = builder.query(&[("pageToken", &req.page_token)]);
         let builder = req
             .instance_partition_deadline
-            .iter()
-            .try_fold(builder, |builder, p| {
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
                 use gax::query_parameter::QueryParameter;
-                serde_json::to_value(p)
-                    .map_err(Error::serde)?
-                    .add(builder, "instancePartitionDeadline")
-                    .map_err(Error::other)
-            })?;
+                v.add(builder, "instancePartitionDeadline")
+            });
         self.inner
             .execute(builder, None::<gax::http_client::NoBody>, options)
             .await
@@ -260,13 +260,16 @@ impl crate::traits::InstanceAdmin for InstanceAdmin {
                 "x-goog-api-client",
                 reqwest::header::HeaderValue::from_static(&crate::info::X_GOOG_API_CLIENT_HEADER),
             );
-        let builder = req.field_mask.iter().try_fold(builder, |builder, p| {
-            use gax::query_parameter::QueryParameter;
-            serde_json::to_value(p)
-                .map_err(Error::serde)?
-                .add(builder, "fieldMask")
-                .map_err(Error::other)
-        })?;
+        let builder = req
+            .field_mask
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
+                use gax::query_parameter::QueryParameter;
+                v.add(builder, "fieldMask")
+            });
         self.inner
             .execute(builder, None::<gax::http_client::NoBody>, options)
             .await
@@ -505,14 +508,14 @@ impl crate::traits::InstanceAdmin for InstanceAdmin {
         let builder = builder.query(&[("pageToken", &req.page_token)]);
         let builder = req
             .instance_partition_deadline
-            .iter()
-            .try_fold(builder, |builder, p| {
+            .as_ref()
+            .map(|p| serde_json::to_value(p).map_err(Error::serde))
+            .transpose()?
+            .into_iter()
+            .fold(builder, |builder, v| {
                 use gax::query_parameter::QueryParameter;
-                serde_json::to_value(p)
-                    .map_err(Error::serde)?
-                    .add(builder, "instancePartitionDeadline")
-                    .map_err(Error::other)
-            })?;
+                v.add(builder, "instancePartitionDeadline")
+            });
         self.inner
             .execute(builder, None::<gax::http_client::NoBody>, options)
             .await