diff --git a/src/openforms/registrations/contrib/objects_api/json_schema.py b/src/openforms/registrations/contrib/objects_api/json_schema.py
index e41a72dbf8..8e454a37b9 100644
--- a/src/openforms/registrations/contrib/objects_api/json_schema.py
+++ b/src/openforms/registrations/contrib/objects_api/json_schema.py
@@ -200,7 +200,7 @@ def json_schema_matches(
     if "string" in target_types and (target_format := target_schema.get("format")):
         variable_format = variable_schema.get("format")
         if variable_format is None:
-            return False
+            return True
         return variable_format == target_format
 
     return True
diff --git a/src/openforms/registrations/contrib/objects_api/tests/test_json_schema.py b/src/openforms/registrations/contrib/objects_api/tests/test_json_schema.py
index 473ff62b1d..88994fe300 100644
--- a/src/openforms/registrations/contrib/objects_api/tests/test_json_schema.py
+++ b/src/openforms/registrations/contrib/objects_api/tests/test_json_schema.py
@@ -434,7 +434,7 @@ def test_json_schema_matches(self):
             variable_schema = {"type": "string"}
             target_schema = {"type": "string", "format": "email"}
 
-            self.assertFalse(
+            self.assertTrue(
                 json_schema_matches(
                     variable_schema=variable_schema, target_schema=target_schema
                 )