diff --git a/backend/services/image_storage.py b/backend/services/image_storage.py
index 5c19f4f6..f20dce8a 100644
--- a/backend/services/image_storage.py
+++ b/backend/services/image_storage.py
@@ -84,8 +84,10 @@ def get_unique_filename(
     # Build the base filename without UUID
     base_filename = f"{sanitized_name}_{variant}.jpg"
 
-    # Check for collision (existing_files should already be lowercased)
-    if base_filename.lower() not in existing_files:
+    # Defensive collision check: handle both pre-lowercased and any-case input
+    # This maintains backward compatibility while supporting the optimization
+    existing_lower = [f.lower() for f in existing_files]
+    if base_filename.lower() not in existing_lower:
         # No collision
         return base_filename