diff --git a/platform/darwin/src/MLNTileSource.h b/platform/darwin/src/MLNTileSource.h
index 9528dfa1e..9ea6b0bcd 100644
--- a/platform/darwin/src/MLNTileSource.h
+++ b/platform/darwin/src/MLNTileSource.h
@@ -211,7 +211,7 @@ MLN_EXPORT
  configuration URL, this is nil until the configuration JSON file
  is loaded.
  */
-@property (nonatomic, copy, readonly) NSString *attributionHTMLString;
+@property (nonatomic, copy, nullable, readonly) NSString *attributionHTMLString;
 
 @end