diff --git a/Scripts/openchange_user_cleanup b/Scripts/openchange_user_cleanup
index e67289480..93a91c8ea 100755
--- a/Scripts/openchange_user_cleanup
+++ b/Scripts/openchange_user_cleanup
@@ -268,6 +268,9 @@ def asCSSIdentifier(inputString):
 
     newChars = []
 
+    if str.isdigit(inputString[0]):
+        newChars.append("_")
+
     for c in inputString:
         if c in cssEscapingCharMap:
             newChars.append(cssEscapingCharMap[c])