diff --git a/ChangeLog b/ChangeLog
index cc6aa74c5..bef7ab731 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-10-12  Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/NSURL.m: Exactly match the percent escaping used by OSX.
+
 2010-10-08  Eric Wasylishen  <ewasylishen@gmail.com>
 
 	* Source/GSAvahiRunLoopIntegration.m: Fix some bugs:
@@ -216,7 +220,7 @@
 	Change sel_getUid to call sel_registerName, in line with OS X
 	behaviour since 10.0
 
-2010-09-02 9avid Chisnall <theraven@gna.org>
+2010-09-02 David Chisnall <theraven@gna.org>
 
 	* Source/NSBundle.m
 	* Source/NSMethodSignature.m
diff --git a/Source/NSURL.m b/Source/NSURL.m
index 36c25937b..36bc003d4 100644
--- a/Source/NSURL.m
+++ b/Source/NSURL.m
@@ -40,6 +40,7 @@ function may be incorrect
 #define	EXPOSE_NSURL_IVARS	1
 #import "Foundation/NSArray.h"
 #import "Foundation/NSCoder.h"
+#import "Foundation/NSData.h"
 #import "Foundation/NSDictionary.h"
 #import "Foundation/NSException.h"
 #import "Foundation/NSFileManager.h"
@@ -54,6 +55,73 @@ function may be incorrect
 NSString * const NSURLErrorDomain = @"NSURLErrorDomain";
 NSString * const NSErrorFailingURLStringKey = @"NSErrorFailingURLStringKey";
 
+@interface	NSString (NSURLPrivate)
+- (NSString*) _stringByAddingPercentEscapes;
+@end
+
+@implementation	NSString (NSURLPrivate)
+/* Like the normal percent escape method, but with additional characters
+ * escaped.
+ */
+- (NSString*) _stringByAddingPercentEscapes
+{
+  NSData	*data = [self dataUsingEncoding: NSUTF8StringEncoding];
+  NSString	*s = nil;
+
+  if (data != nil)
+    {
+      unsigned char	*src = (unsigned char*)[data bytes];
+      unsigned int	slen = [data length];
+      unsigned char	*dst;
+      unsigned int	spos = 0;
+      unsigned int	dpos = 0;
+
+      dst = (unsigned char*)NSZoneMalloc(NSDefaultMallocZone(), slen * 3);
+      while (spos < slen)
+	{
+	  unsigned char	c = src[spos++];
+	  unsigned int	hi;
+	  unsigned int	lo;
+
+	  if (c <= 32
+	    || c > 126
+	    || c == 34
+	    || c == 35
+	    || c == 37
+	    || c == 59
+	    || c == 60
+	    || c == 62
+	    || c == 63
+	    || c == 91
+	    || c == 92
+	    || c == 93
+	    || c == 94
+	    || c == 96
+	    || c == 123
+	    || c == 124
+	    || c == 125)
+	    {
+	      dst[dpos++] = '%';
+	      hi = (c & 0xf0) >> 4;
+	      dst[dpos++] = (hi > 9) ? 'A' + hi - 10 : '0' + hi;
+	      lo = (c & 0x0f);
+	      dst[dpos++] = (lo > 9) ? 'A' + lo - 10 : '0' + lo;
+	    }
+	  else
+	    {
+	      dst[dpos++] = c;
+	    }
+	}
+      s = [[NSString alloc] initWithBytes: dst
+				   length: dpos
+				 encoding: NSASCIIStringEncoding];
+      NSZoneFree(NSDefaultMallocZone(), dst);
+      IF_NO_GC([s autorelease];)
+    }
+  return s;
+}
+@end
+
 /*
  * Structure describing a URL.
  * All the char* fields may be NULL pointers, except path, which
@@ -542,8 +610,7 @@ static unsigned	urlAlign;
 {
   NSString	*aUrlString = [NSString alloc];
 
-  aPath
-    = [aPath stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
+  aPath = [aPath _stringByAddingPercentEscapes];
   if ([aHost length] > 0)
     {
       NSRange	r = [aHost rangeOfString: @"@"];