diff --git a/SDWebImage/SDWebImageManager.m b/SDWebImage/SDWebImageManager.m
index 2781ec8..e545a84 100644
--- a/SDWebImage/SDWebImageManager.m
+++ b/SDWebImage/SDWebImageManager.m
@@ -283,8 +283,9 @@ - (void)saveImageToCache:(UIImage *)image forURL:(NSURL *)url {
 
 - (void)cancelAll {
     @synchronized (self.runningOperations) {
-        [self.runningOperations makeObjectsPerformSelector:@selector(cancel)];
-        [self.runningOperations removeAllObjects];
+        NSArray *copiedOperations = [self.runningOperations copy];
+        [copiedOperations makeObjectsPerformSelector:@selector(cancel)];
+        [self.runningOperations removeObjectsInArray:copiedOperations];
     }
 }