diff --git a/anki/utils.py b/anki/utils.py
index 06be1de67..8b5dc5a7c 100644
--- a/anki/utils.py
+++ b/anki/utils.py
@@ -360,6 +360,8 @@ def invalidFilename(str, dirsep=True):
         return "/"
     elif (dirsep or not isWin) and "\\" in str:
         return "\\"
+    elif str.strip().startswith("."):
+        return "."
 
 def platDesc():
     # we may get an interrupted system call, so try this in a loop