diff --git a/netbox/extras/models.py b/netbox/extras/models.py
index ade251c94..3388f99f9 100644
--- a/netbox/extras/models.py
+++ b/netbox/extras/models.py
@@ -387,7 +387,7 @@ def image_upload(instance, filename):
     path = 'image-attachments/'
 
     # Rename the file to the provided name, if any. Attempt to preserve the file extension.
-    extension = filename.rsplit('.')[-1]
+    extension = filename.rsplit('.')[-1].lower()
     if instance.name and extension in ['bmp', 'gif', 'jpeg', 'jpg', 'png']:
         filename = '.'.join([instance.name, extension])
     elif instance.name: