Build error when replacing deprecated MagicalRecord methods in FTASync

Question

I'm trying to get FTASync working for my iPad app. This is the FTASync code that's giving me a build error and I don't know what's wrong with it. I had to replace a deprecated statement:

[MagicalRecord saveInBackgroundWithBlock:^(localContext)

with the following (first statement; the remainder is original FTASync code)

    [localContext MR_saveToPersistentStoreWithCompletion:^(BOOL success, NSError *error){

    [self syncAll];
}

      completion:^{
          if (self.progressBlock)
              self.progressBlock(1.0, @"Complete");

          if (![NSThread isMainThread]) {
              FSALog(@"%@", @"Completion block must be called on main thread");
          }

          //Use this notification and user defaults key to update an "Last Updated" message in the UI
          [[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:@"FTASyncLastSyncDate"];
          [[NSUserDefaults standardUserDefaults] synchronize];
          dispatch_async(dispatch_get_main_queue(), ^{
              [[NSNotificationCenter defaultCenter] postNotificationName:@"FTASyncDidSync" object:nil];
          });

          if (completion)
              completion();

          self.syncInProgress = NO;
          self.progressBlock = nil;
          self.progress = 0;

          //End background task
          if ([[UIDevice currentDevice] isMultitaskingSupported]) {
              FSCLog(@"Completed sync.");
              [[UIApplication sharedApplication] endBackgroundTask:bgTask];
              bgTask = UIBackgroundTaskInvalid;
          }
      }];

This is the definition of completion:

typedef void (^FTACompletionBlock)(void);

This is the build error I'm getting, which is probably caused by a syntax error somewhere, but I don't see it:

No visible @interface for 'NSManagedObjectContext' declares the selector 'MR_saveToPersistentStoreWithCompletion:completion:'

Can someone tell me what is causing this? and how to fix it?