diff --git a/src/mistralai/models/jsonschema.py b/src/mistralai/models/jsonschema.py
index e2b6a45e..23e163db 100644
--- a/src/mistralai/models/jsonschema.py
+++ b/src/mistralai/models/jsonschema.py
@@ -36,8 +36,10 @@ def serialize_model(self, handler):
 
         for n, f in type(self).model_fields.items():
             k = f.alias or n
-            val = serialized.get(k)
+            # Try alias first, then field name as fallback to handle both by_alias=True and by_alias=False
+            val = serialized.get(k) or serialized.get(n)
             serialized.pop(k, None)
+            serialized.pop(n, None)
 
             optional_nullable = k in optional_fields and k in nullable_fields
             is_set = (
diff --git a/tests/test_jsonschema_serialization.py b/tests/test_jsonschema_serialization.py
new file mode 100644
index 00000000..47417fc7
--- /dev/null
+++ b/tests/test_jsonschema_serialization.py
@@ -0,0 +1,56 @@
+"""Test for JSONSchema serialization with and without by_alias parameter."""
+import json
+from mistralai.extra.utils.response_format import response_format_from_pydantic_model
+from pydantic import BaseModel, Field
+
+
+class TestModel(BaseModel):
+    name: str = Field(description="A name field")
+    value: int = Field(description="A value field")
+
+
+def test_jsonschema_serialization_without_by_alias():
+    """Test that model_dump() works without by_alias=True."""
+    response_format = response_format_from_pydantic_model(TestModel)
+
+    # This should work without by_alias=True
+    serialized = response_format.model_dump(mode='json')
+
+    # Verify that schema is not None
+    assert serialized['json_schema']['schema'] is not None, "Schema should not be None"
+
+    # Verify that schema contains expected fields
+    schema = serialized['json_schema']['schema']
+    assert 'type' in schema
+    assert 'properties' in schema
+    assert 'name' in schema['properties']
+    assert 'value' in schema['properties']
+
+
+def test_jsonschema_serialization_with_by_alias():
+    """Test that model_dump(by_alias=True) continues to work."""
+    response_format = response_format_from_pydantic_model(TestModel)
+
+    # This should work with by_alias=True
+    serialized = response_format.model_dump(mode='json', by_alias=True)
+
+    # Verify that schema is not None
+    assert serialized['json_schema']['schema'] is not None, "Schema should not be None"
+
+    # Verify that schema contains expected fields
+    schema = serialized['json_schema']['schema']
+    assert 'type' in schema
+    assert 'properties' in schema
+    assert 'name' in schema['properties']
+    assert 'value' in schema['properties']
+
+
+def test_jsonschema_serialization_consistency():
+    """Test that both serialization methods produce the same result."""
+    response_format = response_format_from_pydantic_model(TestModel)
+
+    serialized_without_alias = response_format.model_dump(mode='json')
+    serialized_with_alias = response_format.model_dump(mode='json', by_alias=True)
+
+    # Both should produce the same schema
+    assert serialized_without_alias['json_schema']['schema'] == serialized_with_alias['json_schema']['schema']