diff --git a/SDWebImage/SDWebImageDownloader.h b/SDWebImage/SDWebImageDownloader.h
index f1bcc8e9..f4e3830f 100644
--- a/SDWebImage/SDWebImageDownloader.h
+++ b/SDWebImage/SDWebImageDownloader.h
@@ -85,8 +85,10 @@ typedef NS_OPTIONS(NSUInteger, SDWebImageDownloaderOptions) {
     SDWebImageDownloaderPreloadAllFrames = 1 << 11
 };
 
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadStartNotification;
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadStopNotification;
+FOUNDATION_EXPORT NSNotificationName _Nonnull const SDWebImageDownloadStartNotification;
+FOUNDATION_EXPORT NSNotificationName _Nonnull const SDWebImageDownloadReceiveResponseNotification;
+FOUNDATION_EXPORT NSNotificationName _Nonnull const SDWebImageDownloadStopNotification;
+FOUNDATION_EXPORT NSNotificationName _Nonnull const SDWebImageDownloadFinishNotification;
 
 typedef SDImageLoaderProgressBlock SDWebImageDownloaderProgressBlock;
 typedef SDImageLoaderCompletedBlock SDWebImageDownloaderCompletedBlock;
diff --git a/SDWebImage/SDWebImageDownloader.m b/SDWebImage/SDWebImageDownloader.m
index 155a16e5..6ae608f9 100644
--- a/SDWebImage/SDWebImageDownloader.m
+++ b/SDWebImage/SDWebImageDownloader.m
@@ -11,6 +11,11 @@
 #import "SDWebImageDownloaderOperation.h"
 #import "SDWebImageError.h"
 
+NSNotificationName const SDWebImageDownloadStartNotification = @"SDWebImageDownloadStartNotification";
+NSNotificationName const SDWebImageDownloadReceiveResponseNotification = @"SDWebImageDownloadReceiveResponseNotification";
+NSNotificationName const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNotification";
+NSNotificationName const SDWebImageDownloadFinishNotification = @"SDWebImageDownloadFinishNotification";
+
 static void * SDWebImageDownloaderContext = &SDWebImageDownloaderContext;
 
 @interface SDWebImageDownloadToken ()
diff --git a/SDWebImage/SDWebImageDownloaderOperation.h b/SDWebImage/SDWebImageDownloaderOperation.h
index 01b7ea6d..b660771f 100644
--- a/SDWebImage/SDWebImageDownloaderOperation.h
+++ b/SDWebImage/SDWebImageDownloaderOperation.h
@@ -10,13 +10,6 @@
 #import "SDWebImageDownloader.h"
 #import "SDWebImageOperation.h"
 
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadStartNotification;
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadReceiveResponseNotification;
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadStopNotification;
-FOUNDATION_EXPORT NSString * _Nonnull const SDWebImageDownloadFinishNotification;
-
-
-
 /**
  Describes a downloader operation. If one wants to use a custom downloader op, it needs to inherit from `NSOperation` and conform to this protocol
  For the description about these methods, see `SDWebImageDownloaderOperation`
diff --git a/SDWebImage/SDWebImageDownloaderOperation.m b/SDWebImage/SDWebImageDownloaderOperation.m
index 39aad9cd..c3dc3693 100644
--- a/SDWebImage/SDWebImageDownloaderOperation.m
+++ b/SDWebImage/SDWebImageDownloaderOperation.m
@@ -16,11 +16,6 @@ const float NSURLSessionTaskPriorityDefault = 0.5;
 const float NSURLSessionTaskPriorityLow = 0.25;
 #endif
 
-NSString *const SDWebImageDownloadStartNotification = @"SDWebImageDownloadStartNotification";
-NSString *const SDWebImageDownloadReceiveResponseNotification = @"SDWebImageDownloadReceiveResponseNotification";
-NSString *const SDWebImageDownloadStopNotification = @"SDWebImageDownloadStopNotification";
-NSString *const SDWebImageDownloadFinishNotification = @"SDWebImageDownloadFinishNotification";
-
 static NSString *const kProgressCallbackKey = @"progress";
 static NSString *const kCompletedCallbackKey = @"completed";