diff --git a/src/mux_h2.c b/src/mux_h2.c
index bceabf1..a02e138 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -2190,7 +2190,11 @@
 	 * notify the stream about any change.
 	 */
 	if (!h2s->cs) {
-		error = H2_ERR_STREAM_CLOSED;
+		/* The upper layer has already closed, this may happen on
+		 * 4xx/redirects during POST, or when receiving a response
+		 * from an H2 server after the client has aborted.
+		 */
+		error = H2_ERR_CANCEL;
 		goto strm_err;
 	}