diff --git a/common/image_io.py b/common/image_io.py
index 48a249f..fa7e554 100644
--- a/common/image_io.py
+++ b/common/image_io.py
@@ -102,7 +102,12 @@ def fetch_url_bytes(url: str, timeout: float = 10.0, max_bytes: int = DEFAULT_MA
 
                 content_type = (r.headers.get("content-type") or "").lower()
                 if content_type and not content_type.startswith("image/"):
-                    raise ImageLoadError(f"URL does not point to an image content type: {content_type}")
+                    raise _error(
+                        f"URL does not point to an image content type: {content_type}",
+                        category="invalid_content_type",
+                        stage="fetch",
+                        metadata={"content_type": content_type, "remote_status": r.status_code},
+                    )
 
                 buf = io.BytesIO()
                 total = 0