diff --git a/AsyncDisplayKit/ASNetworkImageNode.h b/AsyncDisplayKit/ASNetworkImageNode.h
index 125782bc37..0f984eea37 100644
--- a/AsyncDisplayKit/ASNetworkImageNode.h
+++ b/AsyncDisplayKit/ASNetworkImageNode.h
@@ -51,17 +51,18 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * The image to display.
  *
- * @discussion Setting an image to the image property of an ASNetworkImageNode will cause it to act like a plain
- * ASImageNode if a URL is not set as well. As soon as the URL is set the ASNetworkImageNode will act like an 
- * ASNetworkImageNode and the image property will be managed internally. This means the image property will be cleared
- * out and replaced by the placeholder (<defaultImage>) image while loading and the final image after the new image 
- * data was downloaded and processed. If you want to use a placholder image, use the defaultImage property 
- * instead.
+ * @discussion By setting an image to the image property the ASNetworkImageNode will act like a plain ASImageNode.
+ * As soon as the URL is set the ASNetworkImageNode will act like an ASNetworkImageNode and the image property
+ * will be managed internally. This means the image property will be cleared out and replaced by the placeholder 
+ * (<defaultImage>) image while loading and the final image after the new image data was downloaded and processed.
+ * If you want to use a placholder image functionality use the defaultImage property instead.
  */
 @property (nullable, nonatomic, strong) UIImage *image;
 
 /**
- * A placeholder image to display while the URL is loading.
+ * A placeholder image to display while the URL is loading. This is slightly different than placeholderImage in the
+ * ASDisplayNode superclass as defaultImage will *not* be displayed synchronously. If you wish to have the image
+ * displayed synchronously, use @c placeholderImage.
  */
 @property (nullable, nonatomic, strong, readwrite) UIImage *defaultImage;
 
diff --git a/AsyncDisplayKit/ASNetworkImageNode.mm b/AsyncDisplayKit/ASNetworkImageNode.mm
index 8b090d581a..ac6a7ff4a9 100755
--- a/AsyncDisplayKit/ASNetworkImageNode.mm
+++ b/AsyncDisplayKit/ASNetworkImageNode.mm
@@ -114,7 +114,12 @@ static const CGSize kMinReleaseImageOnBackgroundSize = {20.0, 20.0};
 {
   ASDN::MutexLocker l(__instanceLock__);
   
-  _imageWasSetExternally = (image != nil && _URL == nil);
+  _imageWasSetExternally = (image != nil);
+  if (_imageWasSetExternally) {
+    ASDisplayNodeAssertNil(_URL, @"Directly setting an image on an ASNetworkImageNode causes it to behave like an ASImageNode instead of an ASNetworkImageNode. If this is what you want, set the URL to nil first.");
+    [self _cancelDownloadAndClearImage];
+    _URL = nil;
+  }
   
   [self _setImage:image];
 }
@@ -134,6 +139,8 @@ static const CGSize kMinReleaseImageOnBackgroundSize = {20.0, 20.0};
   {
     ASDN::MutexLocker l(__instanceLock__);
     
+    ASDisplayNodeAssert(_imageWasSetExternally == NO, @"Setting a URL to an ASNetworkImageNode after setting an image changes its behavior from an ASImageNode to an ASNetworkImageNode. If this is what you want, set the image to nil first.");
+    
     _imageWasSetExternally = NO;
     
     if (ASObjectIsEqual(URL, _URL)) {