diff --git a/src/snapshots/client.py b/src/snapshots/client.py
index 4e6dbca..3c1a337 100644
--- a/src/snapshots/client.py
+++ b/src/snapshots/client.py
@@ -74,6 +74,8 @@ def fetch_url(base: str, url: str) -> str | None:
             if len(content) > 2_500_000:
                 return None
         content_type = response.headers.get("Content-Type", "")
+        if content_type == "":
+            return None
         return encode_data_uri(content, content_type)
     except requests.exceptions.RequestException:
         return None