diff --git a/src/graphql/execution/execute.py b/src/graphql/execution/execute.py
index 4ddff2ad..d6e7fea2 100644
--- a/src/graphql/execution/execute.py
+++ b/src/graphql/execution/execute.py
@@ -315,7 +315,9 @@ async def build_response_async():
             return ExecutionResult(data, None)
         # Sort the error list in order to make it deterministic, since we might have
         # been using parallel execution.
-        errors.sort(key=lambda error: (error.locations, error.path, error.message))
+        errors.sort(
+            key=lambda error: (error.locations or [], error.path or [], error.message)
+        )
         return ExecutionResult(data, errors)
 
     def execute_operation(