diff --git a/mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m b/mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m
index 8dc3b8a356..6355ddc008 100644
--- a/mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m
+++ b/mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m
@@ -91,8 +91,17 @@ typedef enum {
             NSUInteger index = NSNotFound;
             if ((index = [value rangeOfString:@"filename="].location) != NSNotFound)
                 _downloadFilename = [NSString stringWithString:[value substringFromIndex:index+9]];
-            else if ((index = [value rangeOfString:@"url="].location) != NSNotFound)
-                downloadUrl = [NSURL URLWithString:[[NSString stringWithString:[value substringFromIndex:index+4]] stringByRemovingPercentEncoding]];
+            else if ((index = [value rangeOfString:@"url="].location) != NSNotFound) {
+                NSString *urlString = [NSString stringWithString:[value substringFromIndex:index+4]];
+                @try {
+                    urlString = [urlString stringByRemovingPercentEncoding];
+                }
+                @catch (NSException *e) {
+                    // Must be an OS version prior to 10.9 - try this (now deprecated) method instead:
+                    urlString = [urlString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
+                }
+                downloadUrl = [NSURL URLWithString:urlString];
+            }
         }
         
         if (downloadUrl && _downloadFilename) {