diff --git a/ChangeLog b/ChangeLog
index a1c8dcb32..b3e55e433 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2009-07-27  David Ayers  <ayers@fsfe.org>
+
+	* Source/Additions/GSCompatibility.m ([-boolValue]): Only compile
+	for OS X Versions below 10.5 and sync implementation with -base.
+	Reported by: Georg Fleischmann
+	
 2009-07-23 Richard Frith-Macdonald <rfm@gnu.org>
 
 	* GSHTTPURLHandle.m:
diff --git a/Source/Additions/GSCompatibility.m b/Source/Additions/GSCompatibility.m
index 5a64a8463..7c1e9e210 100644
--- a/Source/Additions/GSCompatibility.m
+++ b/Source/Additions/GSCompatibility.m
@@ -394,24 +394,30 @@ BOOL GSDebugSet(NSString *level)
 
 @implementation NSString(GSCompatibility)
 
-// From GNUStep
+#ifndef MAC_OS_X_VERSION_10_5
 /**
- * If the string consists of the words 'true' or 'yes' (case insensitive)
- * or begins with a non-zero numeric value, return YES, otherwise return
- * NO.
+ * Returns YES when scanning the receiver's text from left to right finds a
+ * digit in the range 1-9 or a letter in the set ('Y', 'y', 'T', 't').<br />
+ * Any trailing characters are ignored.<br />
+ * Any leading whitespace or zeros or signs are also ignored.<br />
+ * Returns NO if the above conditions are not met.
  */
 - (BOOL) boolValue
 {
-  if ([self caseInsensitiveCompare: @"YES"] == NSOrderedSame)
+  static NSCharacterSet *yes = nil;
+
+  if (yes == nil)
     {
-        return YES;
+      yes = RETAIN([NSCharacterSet characterSetWithCharactersInString:
+      @"123456789yYtT"]);
     }
-  if ([self caseInsensitiveCompare: @"true"] == NSOrderedSame)
+  if ([self rangeOfCharacterFromSet: yes].length > 0)
     {
-        return YES;
+      return YES;
     }
-  return [self intValue] != 0 ? YES : NO;
+  return NO;
 }
+#endif
 
 - (NSString*) substringFromRange:(NSRange)range
 {