diff --git a/SDWebImage/SDWebImageDownloader.h b/SDWebImage/SDWebImageDownloader.h
index adb24cb..d9dd3de 100644
--- a/SDWebImage/SDWebImageDownloader.h
+++ b/SDWebImage/SDWebImageDownloader.h
@@ -57,7 +57,7 @@ typedef enum
 extern NSString *const SDWebImageDownloadStartNotification;
 extern NSString *const SDWebImageDownloadStopNotification;
 
-typedef void(^SDWebImageDownloaderProgressBlock)(NSUInteger receivedSize, NSUInteger expectedSize);
+typedef void(^SDWebImageDownloaderProgressBlock)(NSInteger receivedSize, NSInteger expectedSize);
 typedef void(^SDWebImageDownloaderCompletedBlock)(UIImage *image, NSData *data, NSError *error, BOOL finished);
 
 /**
diff --git a/SDWebImage/SDWebImageDownloader.m b/SDWebImage/SDWebImageDownloader.m
index 6f8ab90..a6e6ed8 100644
--- a/SDWebImage/SDWebImageDownloader.m
+++ b/SDWebImage/SDWebImageDownloader.m
@@ -115,7 +115,7 @@ static NSString *const kCompletedCallbackKey = @"completed";
     return _downloadQueue.maxConcurrentOperationCount;
 }
 
-- (id<SDWebImageOperation>)downloadImageWithURL:(NSURL *)url options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSUInteger, NSUInteger))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock
+- (id<SDWebImageOperation>)downloadImageWithURL:(NSURL *)url options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSInteger, NSInteger))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock
 {
     __block SDWebImageDownloaderOperation *operation;
     __weak SDWebImageDownloader *wself = self;
@@ -139,7 +139,7 @@ static NSString *const kCompletedCallbackKey = @"completed";
         {
             request.allHTTPHeaderFields = wself.HTTPHeaders;
         }
-        operation = [SDWebImageDownloaderOperation.alloc initWithRequest:request options:options progress:^(NSUInteger receivedSize, NSUInteger expectedSize)
+        operation = [SDWebImageDownloaderOperation.alloc initWithRequest:request options:options progress:^(NSInteger receivedSize, NSInteger expectedSize)
         {
             if (!wself) return;
             SDWebImageDownloader *sself = wself;
@@ -183,7 +183,7 @@ static NSString *const kCompletedCallbackKey = @"completed";
     return operation;
 }
 
-- (void)addProgressCallback:(void (^)(NSUInteger, NSUInteger))progressBlock andCompletedBlock:(void (^)(UIImage *, NSData *data, NSError *, BOOL))completedBlock forURL:(NSURL *)url createCallback:(void (^)())createCallback
+- (void)addProgressCallback:(void (^)(NSInteger, NSInteger))progressBlock andCompletedBlock:(void (^)(UIImage *, NSData *data, NSError *, BOOL))completedBlock forURL:(NSURL *)url createCallback:(void (^)())createCallback
 {
     // The URL will be used as the key to the callbacks dictionary so it cannot be nil. If it is nil immediately call the completed block with no image or data.
     if(url == nil)
diff --git a/SDWebImage/SDWebImageDownloaderOperation.m b/SDWebImage/SDWebImageDownloaderOperation.m
index 38d7702..e886fb5 100644
--- a/SDWebImage/SDWebImageDownloaderOperation.m
+++ b/SDWebImage/SDWebImageDownloaderOperation.m
@@ -19,7 +19,7 @@
 
 @property (assign, nonatomic, getter = isExecuting) BOOL executing;
 @property (assign, nonatomic, getter = isFinished) BOOL finished;
-@property (assign, nonatomic) NSUInteger expectedSize;
+@property (assign, nonatomic) NSInteger expectedSize;
 @property (strong, nonatomic) NSMutableData *imageData;
 @property (strong, nonatomic) NSURLConnection *connection;
 @property (strong, atomic) NSThread *thread;
@@ -36,7 +36,7 @@
     BOOL responseFromCached;
 }
 
-- (id)initWithRequest:(NSURLRequest *)request options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSUInteger, NSUInteger))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock cancelled:(void (^)())cancelBlock
+- (id)initWithRequest:(NSURLRequest *)request options:(SDWebImageDownloaderOptions)options progress:(void (^)(NSInteger, NSInteger))progressBlock completed:(void (^)(UIImage *, NSData *, NSError *, BOOL))completedBlock cancelled:(void (^)())cancelBlock
 {
     if ((self = [super init]))
     {
@@ -94,7 +94,7 @@
     {
         if (self.progressBlock)
         {
-            self.progressBlock(0, -1);
+            self.progressBlock(0, NSURLResponseUnknownLength);
         }
         [[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStartNotification object:self];
 
@@ -208,7 +208,7 @@
 {
     if (![response respondsToSelector:@selector(statusCode)] || [((NSHTTPURLResponse *)response) statusCode] < 400)
     {
-        NSUInteger expected = response.expectedContentLength > 0 ? (NSUInteger)response.expectedContentLength : 0;
+        NSInteger expected = response.expectedContentLength > 0 ? (NSInteger)response.expectedContentLength : 0;
         self.expectedSize = expected;
         if (self.progressBlock)
         {
@@ -242,7 +242,7 @@
         // Thanks to the author @Nyx0uf
 
         // Get the total bytes downloaded
-        const NSUInteger totalSize = self.imageData.length;
+        const NSInteger totalSize = self.imageData.length;
 
         // Update the data source, we must pass ALL the data, not just the new bytes
         CGImageSourceRef imageSource = CGImageSourceCreateIncremental(NULL);