diff --git a/ext/assrender/gstassrender.c b/ext/assrender/gstassrender.c
index f4cf5e2dc3..1845f8b128 100644
--- a/ext/assrender/gstassrender.c
+++ b/ext/assrender/gstassrender.c
@@ -1024,6 +1024,7 @@ gst_ass_render_chain_video (GstPad * pad, GstBuffer * buffer)
       return ret;
     }
 
+    buffer = gst_buffer_make_writable (buffer);
     render->blit (render, ass_image, buffer);
   }