diff --git a/starpunk/media.py b/starpunk/media.py
index 2a8073a..1b650da 100644
--- a/starpunk/media.py
+++ b/starpunk/media.py
@@ -170,7 +170,15 @@ def validate_image(file_data: bytes, filename: str) -> Tuple[bytes, str, int, in
             mime_type = 'image/jpeg'
 
         if mime_type not in ALLOWED_MIME_TYPES:
-            raise ValueError(f"Invalid image format. Accepted: JPEG, PNG, GIF, WebP")
+            # Log the detected format for debugging (v1.4.2)
+            try:
+                current_app.logger.warning(
+                    f'Media upload rejected format: filename="{filename}", '
+                    f'detected_format="{img.format}", mime_type="{mime_type}"'
+                )
+            except RuntimeError:
+                pass  # Outside app context
+            raise ValueError(f"Invalid image format '{img.format}'. Accepted: JPEG, PNG, GIF, WebP")
     else:
         raise ValueError("Could not determine image format")