diff --git a/gql/transport/aiohttp.py b/gql/transport/aiohttp.py
index e6e3a782..2b155870 100644
--- a/gql/transport/aiohttp.py
+++ b/gql/transport/aiohttp.py
@@ -325,6 +325,9 @@ async def raise_response_error(resp: aiohttp.ClientResponse, reason: str):
             except Exception:
                 await raise_response_error(resp, "Not a JSON answer")
 
+            if result is None:
+                await raise_response_error(resp, "Not a JSON answer")
+
             if "errors" not in result and "data" not in result:
                 await raise_response_error(resp, 'No "data" or "errors" keys in answer')
 
diff --git a/tests/test_aiohttp.py b/tests/test_aiohttp.py
index f4899c82..d78e4333 100644
--- a/tests/test_aiohttp.py
+++ b/tests/test_aiohttp.py
@@ -299,6 +299,12 @@ async def handler(request):
             'No "data" or "errors" keys in answer: {"not_data_or_errors": 35}'
         ),
     },
+    {
+        "response": "",
+        "expected_exception": (
+            "Server did not return a GraphQL result: Not a JSON answer: "
+        ),
+    },
 ]