diff --git a/SDWebImage/SDWebImageDownloader.m b/SDWebImage/SDWebImageDownloader.m
index ac552219..be1a9e92 100644
--- a/SDWebImage/SDWebImageDownloader.m
+++ b/SDWebImage/SDWebImageDownloader.m
@@ -151,8 +151,8 @@ NSString *const kCompletedCallbackKey = @"completed";
         // Handle single download of simultaneous download request for the same URL
         NSMutableArray *callbacksForURL = self.URLCallbacks[url];
         NSMutableDictionary *callbacks = NSMutableDictionary.new;
-        if (progressBlock) callbacks[kProgressCallbackKey] = progressBlock;
-        if (completedBlock) callbacks[kCompletedCallbackKey] = completedBlock;
+        if (progressBlock) callbacks[kProgressCallbackKey] = [progressBlock copy];
+        if (completedBlock) callbacks[kCompletedCallbackKey] = [completedBlock copy];
         [callbacksForURL addObject:callbacks];
         self.URLCallbacks[url] = callbacksForURL;
 
diff --git a/SDWebImage/SDWebImageDownloaderOperation.m b/SDWebImage/SDWebImageDownloaderOperation.m
index 8e0304c8..0af2733d 100644
--- a/SDWebImage/SDWebImageDownloaderOperation.m
+++ b/SDWebImage/SDWebImageDownloaderOperation.m
@@ -12,9 +12,9 @@
 
 @interface SDWebImageDownloaderOperation ()
 
-@property (strong, nonatomic) SDWebImageDownloaderProgressBlock progressBlock;
-@property (strong, nonatomic) SDWebImageDownloaderCompletedBlock completedBlock;
-@property (strong, nonatomic) void (^cancelBlock)();
+@property (copy, nonatomic) SDWebImageDownloaderProgressBlock progressBlock;
+@property (copy, nonatomic) SDWebImageDownloaderCompletedBlock completedBlock;
+@property (copy, nonatomic) void (^cancelBlock)();
 
 @property (assign, nonatomic, getter = isExecuting) BOOL executing;
 @property (assign, nonatomic, getter = isFinished) BOOL finished;
@@ -37,9 +37,9 @@
         _queue = queue;
         _request = request;
         _options = options;
-        _progressBlock = progressBlock;
-        _completedBlock = completedBlock;
-        _cancelBlock = cancelBlock;
+        _progressBlock = [progressBlock copy];
+        _completedBlock = [completedBlock copy];
+        _cancelBlock = [cancelBlock copy];
         _executing = NO;
         _finished = NO;
         _expectedSize = 0;
diff --git a/SDWebImage/SDWebImageManager.m b/SDWebImage/SDWebImageManager.m
index 58971724..4e3e6a4c 100644
--- a/SDWebImage/SDWebImageManager.m
+++ b/SDWebImage/SDWebImageManager.m
@@ -12,7 +12,7 @@
 @interface SDWebImageCombinedOperation : NSObject <SDWebImageOperation>
 
 @property (assign, nonatomic, getter = isCancelled) BOOL cancelled;
-@property (strong, nonatomic) void (^cancelBlock)();
+@property (copy, nonatomic) void (^cancelBlock)();
 
 @end
 
@@ -146,7 +146,7 @@
     }
     else
     {
-        _cancelBlock = cancelBlock;
+        _cancelBlock = [cancelBlock copy];
     }
 }