diff --git a/SDWebImage/UIView+WebCacheOperation.m b/SDWebImage/UIView+WebCacheOperation.m
index d83c8e0c..5be2b03e 100644
--- a/SDWebImage/UIView+WebCacheOperation.m
+++ b/SDWebImage/UIView+WebCacheOperation.m
@@ -31,9 +31,11 @@ typedef NSMapTable<NSString *, id<SDWebImageOperation>> SDOperationsDictionary;
 
 - (nullable id<SDWebImageOperation>)sd_imageLoadOperationForKey:(nullable NSString *)key  {
     id<SDWebImageOperation> operation;
-    SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];
-    @synchronized (self) {
-        operation = [operationDictionary objectForKey:key];
+    if (key) {
+        SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];
+        @synchronized (self) {
+            operation = [operationDictionary objectForKey:key];
+        }
     }
     return operation;
 }