diff --git a/testbench/error.py b/testbench/error.py
index aee4c159..5afe3228 100644
--- a/testbench/error.py
+++ b/testbench/error.py
@@ -29,7 +29,13 @@ def __init__(self, msg, code):
         self.code = code
 
     def as_response(self):
-        return flask.make_response(flask.jsonify(self.msg), self.code)
+        # Include both code and message so we follow the schema outlined in
+        # https://cloud.google.com/apis/design/errors#error_model and some
+        # clients depend on code being specified, otherwise behavior is
+        # undefined.
+        return flask.make_response(
+            flask.jsonify(code=self.code, message=self.msg), self.code
+        )
 
     @staticmethod
     def handler(ex):