diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index e739d8a4..6455aec9 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -1309,6 +1309,7 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
       if (error_reply(downstream, 500) != 0) {
         return -1;
       }
+      // Returning -1 will signal deletion of dconn.
       return -1;
     }
 
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index bc60915e..0be56597 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -952,6 +952,7 @@ int SpdyUpstream::on_downstream_header_complete(Downstream *downstream) {
     if (error_reply(downstream, 500) != 0) {
       return -1;
     }
+    // Returning -1 will signal deletion of dconn.
     return -1;
   }