diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index 314538fa..50c40e11 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -879,8 +879,13 @@ typedef int (*nghttp2_on_frame_send_callback)
  * sent because of the error. The error is indicated by the
  * |lib_error_code|, which is one of the values defined in
  * :type:`nghttp2_error`.
+ *
+ * The implementation of this function must return 0 if it
+ * succeeds. If nonzero is returned, it is treated as fatal error and
+ * `nghttp2_session_recv()` and `nghttp2_session_send()` functions
+ * immediately return :enum:`NGHTTP2_ERR_CALLBACK_FAILURE`.
  */
-typedef void (*nghttp2_on_frame_not_send_callback)
+typedef int (*nghttp2_on_frame_not_send_callback)
 (nghttp2_session *session, nghttp2_frame *frame, int lib_error_code,
  void *user_data);
 
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index 4e2da2b6..5ade5e8a 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -1474,8 +1474,10 @@ int nghttp2_session_send(nghttp2_session *session)
              it. */
           nghttp2_frame *frame = nghttp2_outbound_item_get_ctrl_frame(item);
           if(frame->hd.type != NGHTTP2_WINDOW_UPDATE) {
-            session->callbacks.on_frame_not_send_callback
-              (session, frame, framebuflen, session->user_data);
+            if(session->callbacks.on_frame_not_send_callback
+               (session, frame, framebuflen, session->user_data) != 0) {
+              return NGHTTP2_ERR_CALLBACK_FAILURE;
+            }
           }
         }
         nghttp2_outbound_item_free(item);
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index 4269416d..95a39a42 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -331,9 +331,9 @@ int on_data_chunk_recv_callback(nghttp2_session *session,
 } // namespace
 
 namespace {
-void on_frame_not_send_callback(nghttp2_session *session,
-                                nghttp2_frame *frame,
-                                int lib_error_code, void *user_data)
+int on_frame_not_send_callback(nghttp2_session *session,
+                               nghttp2_frame *frame,
+                               int lib_error_code, void *user_data)
 {
   auto upstream = reinterpret_cast<Http2Upstream*>(user_data);
   ULOG(WARNING, upstream) << "Failed to send control frame type="
@@ -348,6 +348,7 @@ void on_frame_not_send_callback(nghttp2_session *session,
       upstream->rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
     }
   }
+  return 0;
 }
 } // namespace
 
diff --git a/src/shrpx_spdy_session.cc b/src/shrpx_spdy_session.cc
index 12c87ab1..d2e3e92c 100644
--- a/src/shrpx_spdy_session.cc
+++ b/src/shrpx_spdy_session.cc
@@ -970,7 +970,7 @@ int before_frame_send_callback(nghttp2_session *session,
 } // namespace
 
 namespace {
-void on_frame_not_send_callback(nghttp2_session *session,
+int on_frame_not_send_callback(nghttp2_session *session,
                                 nghttp2_frame *frame,
                                 int lib_error_code, void *user_data)
 {
@@ -986,19 +986,20 @@ void on_frame_not_send_callback(nghttp2_session *session,
     auto sd = reinterpret_cast<StreamData*>
       (nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
     if(!sd) {
-      return;
+      return 0;
     }
     if(sd->dconn) {
       auto downstream = sd->dconn->get_downstream();
       if(!downstream ||
          downstream->get_downstream_stream_id() != frame->hd.stream_id) {
-        return;
+        return 0;
       }
       downstream->set_response_state(Downstream::MSG_RESET);
       call_downstream_readcb(spdy, downstream);
     }
     spdy->remove_stream_data(sd);
   }
+  return 0;
 }
 } // namespace
 
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index 32ef3166..aa4dc33c 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -155,15 +155,16 @@ static int on_frame_send_callback(nghttp2_session *session,
   return 0;
 }
 
-static void on_frame_not_send_callback(nghttp2_session *session,
-                                       nghttp2_frame *frame,
-                                       int lib_error,
-                                       void *user_data)
+static int on_frame_not_send_callback(nghttp2_session *session,
+                                      nghttp2_frame *frame,
+                                      int lib_error,
+                                      void *user_data)
 {
   my_user_data *ud = (my_user_data*)user_data;
   ++ud->frame_not_send_cb_called;
   ud->not_sent_frame_type = frame->hd.type;
   ud->not_sent_error = lib_error;
+  return 0;
 }
 
 static int on_data_chunk_recv_callback(nghttp2_session *session,