diff --git a/SDWebImage/SDWebImageManager.m b/SDWebImage/SDWebImageManager.m
index 2e893ec..b4361a0 100644
--- a/SDWebImage/SDWebImageManager.m
+++ b/SDWebImage/SDWebImageManager.m
@@ -191,6 +191,10 @@
             }];
             operation.cancelBlock = ^{
                 [subOperation cancel];
+                
+                @synchronized (self.runningOperations) {
+                    [self.runningOperations removeObject:weakOperation];
+                }
             };
         }
         else if (image) {