diff --git a/libswscale/swscale.h b/libswscale/swscale.h
index ff3f630ec1..da9dd2ea8f 100644
--- a/libswscale/swscale.h
+++ b/libswscale/swscale.h
@@ -150,6 +150,7 @@ struct SwsContext *sws_alloc_context(void);
  * @return zero or positive value on success, a negative value on
  * error
  */
+av_warn_unused_result
 int sws_init_context(struct SwsContext *sws_context, SwsFilter *srcFilter, SwsFilter *dstFilter);
 
 /**