diff --git a/SoObjects/SOGo/NSString+Utilities.m b/SoObjects/SOGo/NSString+Utilities.m
index 4d8acf863..75ee19d21 100644
--- a/SoObjects/SOGo/NSString+Utilities.m
+++ b/SoObjects/SOGo/NSString+Utilities.m
@@ -134,8 +134,9 @@ static NSMutableCharacterSet *urlAfterEndingChars = nil;
     length = endRange.location;
   length -= start;
   while
-    ([urlNonEndingChars characterIsMember:
-			  [self characterAtIndex: (start + length - 1)]])
+    (length > 0
+     && [urlNonEndingChars characterIsMember:
+			     [self characterAtIndex: (start + length - 1)]])
     length--;
 
   return NSMakeRange (start, length);