diff --git a/JOYNAT/__init__.py b/JOYNAT/__init__.py
index 3287279..62724c9 100644
--- a/JOYNAT/__init__.py
+++ b/JOYNAT/__init__.py
@@ -416,7 +416,7 @@ class JOYNAT(Service):
         self, *, challenge: bytes, title: Union[Movies, Series], track: AnyTrack,
     ) -> Optional[Union[bytes, str]]:
         """Obtain a Widevine license for the given track."""
-        license_url = getattr(track, 'data', {}).get('license_url') if track.data else None
+        license_url = track.data.get('license_url')
         if not license_url:
             raise ValueError("No license_url in track.data.")
 
@@ -441,7 +441,7 @@ class JOYNAT(Service):
             },
             params={
                 'operationName': operation_name,
-                'variables': json.dumps(variables).encode(),
+                'variables': json.dumps(variables),
                 'extensions': json.dumps({
                     'persistedQuery': {'version': 1, 'sha256Hash': persisted_query_hash}
                 }).encode()
@@ -451,6 +451,9 @@ class JOYNAT(Service):
 
         response_data = response.json()
 
+        if response_data.get("errors"):
+            raise ValueError(f"GraphQL errors for '{operation_name}': {response_data['errors']}")
+
         if 'data' not in response_data:
             self.log.error(f"GraphQL response for '{operation_name}' missing 'data' field.")
             raise ValueError(f"Invalid GraphQL response for '{operation_name}'.")
diff --git a/RTLP/__init__.py b/RTLP/__init__.py
index 1d1e0b0..f6bf504 100644
--- a/RTLP/__init__.py
+++ b/RTLP/__init__.py
@@ -437,8 +437,13 @@ class RTLP(Service):
         response.raise_for_status()
 
         response_data = response.json()
+
+        if response_data.get("errors"):
+            raise ValueError(f"GraphQL errors for '{operation_name}': {response_data['errors']}")
+
         if 'data' not in response_data:
-            raise ValueError(f"Invalid GraphQL response for '{operation_name}': missing 'data' field.")
+            self.log.error(f"GraphQL response for '{operation_name}' missing 'data' field.")
+            raise ValueError(f"Invalid GraphQL response for '{operation_name}'.")
 
         return response_data['data']