diff --git a/lib/nghttp2_submit.c b/lib/nghttp2_submit.c
index 14ec7666..763b4038 100644
--- a/lib/nghttp2_submit.c
+++ b/lib/nghttp2_submit.c
@@ -156,10 +156,11 @@ static int32_t submit_headers_shared_nva(nghttp2_session *session,
                                attach_stream);
 }
 
-int32_t nghttp2_submit_trailer(nghttp2_session *session, int32_t stream_id,
-                               const nghttp2_nv *nva, size_t nvlen) {
-  return submit_headers_shared_nva(session, NGHTTP2_FLAG_END_STREAM, stream_id,
-                                   NULL, nva, nvlen, NULL, NULL, 0);
+int nghttp2_submit_trailer(nghttp2_session *session, int32_t stream_id,
+                           const nghttp2_nv *nva, size_t nvlen) {
+  return (int)submit_headers_shared_nva(session, NGHTTP2_FLAG_END_STREAM,
+                                        stream_id, NULL, nva, nvlen, NULL, NULL,
+                                        0);
 }
 
 int32_t nghttp2_submit_headers(nghttp2_session *session, uint8_t flags,