diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3589dd7f..c0162fe2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Return "Unknown specification" error on `https`-prefixed `$schema` for Draft 4, 5, 6. [#629](https://github.com/Stranger6667/jsonschema/issues/629)
+
 ## [0.26.0] - 2024-10-26
 
 **Important:** This release contains breaking changes. See the [Migration Guide](MIGRATION.md) for details on transitioning to the new API.
diff --git a/crates/jsonschema-py/CHANGELOG.md b/crates/jsonschema-py/CHANGELOG.md
index c4f978f1..e5c1fe33 100644
--- a/crates/jsonschema-py/CHANGELOG.md
+++ b/crates/jsonschema-py/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Return "Unknown specification" error on `https`-prefixed `$schema` for Draft 4, 5, 6. [#629](https://github.com/Stranger6667/jsonschema/issues/629)
+
 ### Performance
 
 - Speedup Python -> Rust data serialization.
diff --git a/crates/jsonschema-py/tests-py/test_jsonschema.py b/crates/jsonschema-py/tests-py/test_jsonschema.py
index f367174c..33ec79f2 100644
--- a/crates/jsonschema-py/tests-py/test_jsonschema.py
+++ b/crates/jsonschema-py/tests-py/test_jsonschema.py
@@ -155,6 +155,13 @@ def test_invalid_value(method):
         getattr(schema, method)(object())
 
 
+def test_invalid_schema_keyword():
+    # Note `https`, not `http`
+    schema = {"$schema": "https://json-schema.org/draft-07/schema"}
+    with pytest.raises(ValidationError, match="Unknown specification: https://json-schema.org/draft-07/schema"):
+        validator_for(schema)
+
+
 def test_error_message():
     schema = {"properties": {"foo": {"type": "integer"}}}
     instance = {"foo": None}
diff --git a/crates/jsonschema/src/compiler.rs b/crates/jsonschema/src/compiler.rs
index 1ef998b7..39d93ecf 100644
--- a/crates/jsonschema/src/compiler.rs
+++ b/crates/jsonschema/src/compiler.rs
@@ -285,7 +285,7 @@ pub(crate) fn build_validator(
     mut config: ValidationOptions,
     schema: &Value,
 ) -> Result<Validator, ValidationError<'static>> {
-    let draft = config.draft_for(schema);
+    let draft = config.draft_for(schema)?;
     let resource_ref = draft.create_resource_ref(schema);
     let resource = draft.create_resource(schema.clone());
     let base_uri = resource.id().unwrap_or(DEFAULT_ROOT_URL).to_string();
diff --git a/crates/jsonschema/src/lib.rs b/crates/jsonschema/src/lib.rs
index 867f7674..c59caa2d 100644
--- a/crates/jsonschema/src/lib.rs
+++ b/crates/jsonschema/src/lib.rs
@@ -1335,6 +1335,19 @@ mod tests {
         assert!(validate_fn(&schema, &invalid_instance).is_err());
     }
 
+    #[test]
+    fn test_invalid_schema_keyword() {
+        let schema = json!({
+            // Note `https`, not `http`
+            "$schema": "https://json-schema.org/draft-07/schema",
+        });
+        let error = crate::validator_for(&schema).expect_err("Should fail");
+        assert_eq!(
+            error.to_string(),
+            "Unknown specification: https://json-schema.org/draft-07/schema"
+        );
+    }
+
     #[test_case(Draft::Draft4)]
     #[test_case(Draft::Draft6)]
     #[test_case(Draft::Draft7)]
diff --git a/crates/jsonschema/src/options.rs b/crates/jsonschema/src/options.rs
index 7db51f61..7a6b4fad 100644
--- a/crates/jsonschema/src/options.rs
+++ b/crates/jsonschema/src/options.rs
@@ -55,28 +55,28 @@ impl ValidationOptions {
     pub(crate) fn draft(&self) -> Draft {
         self.draft.unwrap_or_default()
     }
-    pub(crate) fn draft_for(&self, contents: &Value) -> Draft {
+    pub(crate) fn draft_for(&self, contents: &Value) -> Result<Draft, ValidationError<'static>> {
         // Preference:
         //  - Explicitly set
         //  - Autodetected
         //  - Default
         if let Some(draft) = self.draft {
-            draft
+            Ok(draft)
         } else {
             let default = Draft::default();
             match default.detect(contents) {
-                Ok(draft) => draft,
+                Ok(draft) => Ok(draft),
                 Err(referencing::Error::UnknownSpecification { specification }) => {
                     // Try to retrieve the specification and detect its draft
                     if let Ok(Ok(retrieved)) = uri::from_str(&specification)
                         .map(|uri| self.retriever.retrieve(&uri.borrow()))
                     {
-                        default.detect(&retrieved).unwrap_or_default()
+                        Ok(default.detect(&retrieved)?)
                     } else {
-                        default
+                        Err(referencing::Error::UnknownSpecification { specification }.into())
                     }
                 }
-                _ => default,
+                Err(error) => Err(error.into()),
             }
         }
     }