diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 9e36e613..0c446400 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -764,7 +764,7 @@ int hd_on_frame_recv_callback
   auto hd = reinterpret_cast<Http2Handler*>(user_data);
   if(hd->get_config()->verbose) {
     print_session_id(hd->session_id());
-    on_frame_recv_callback(session, frame, user_data);
+    verbose_on_frame_recv_callback(session, frame, user_data);
   }
   switch(frame->hd.type) {
   case NGHTTP2_HEADERS:
@@ -856,7 +856,7 @@ int hd_on_frame_send_callback
   }
   if(hd->get_config()->verbose) {
     print_session_id(hd->session_id());
-    on_frame_send_callback(session, frame, user_data);
+    verbose_on_frame_send_callback(session, frame, user_data);
   }
   return 0;
 }
@@ -881,7 +881,8 @@ int hd_on_data_recv_callback
   auto hd = reinterpret_cast<Http2Handler*>(user_data);
   if(hd->get_config()->verbose) {
     print_session_id(hd->session_id());
-    on_data_recv_callback(session, length, flags, stream_id, user_data);
+    verbose_on_data_recv_callback(session, length, flags, stream_id,
+                                  user_data);
   }
   return 0;
 }
@@ -895,7 +896,8 @@ int hd_on_data_send_callback
   auto hd = reinterpret_cast<Http2Handler*>(user_data);
   if(hd->get_config()->verbose) {
     print_session_id(hd->session_id());
-    on_data_send_callback(session, length, flags, stream_id, user_data);
+    verbose_on_data_send_callback(session, length, flags, stream_id,
+                                  user_data);
   }
   return 0;
 }
@@ -931,10 +933,12 @@ void fill_callback(nghttp2_session_callbacks& callbacks, const Config *config)
   callbacks.on_data_recv_callback = hd_on_data_recv_callback;
   callbacks.on_data_send_callback = hd_on_data_send_callback;
   if(config->verbose) {
-    callbacks.on_invalid_frame_recv_callback = on_invalid_frame_recv_callback;
+    callbacks.on_invalid_frame_recv_callback =
+      verbose_on_invalid_frame_recv_callback;
     callbacks.on_frame_recv_parse_error_callback =
-      on_frame_recv_parse_error_callback;
-    callbacks.on_unknown_frame_recv_callback = on_unknown_frame_recv_callback;
+      verbose_on_frame_recv_parse_error_callback;
+    callbacks.on_unknown_frame_recv_callback =
+      verbose_on_unknown_frame_recv_callback;
   }
   callbacks.on_data_chunk_recv_callback = on_data_chunk_recv_callback;
   callbacks.on_request_recv_callback = config->on_request_recv_callback;
diff --git a/src/app_helper.cc b/src/app_helper.cc
index 859c5a7c..cc9d848f 100644
--- a/src/app_helper.cc
+++ b/src/app_helper.cc
@@ -340,7 +340,7 @@ void print_frame(print_type ptype, const nghttp2_frame *frame)
 }
 } // namespace
 
-int on_frame_recv_callback
+int verbose_on_frame_recv_callback
 (nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
 {
   print_timer();
@@ -350,7 +350,7 @@ int on_frame_recv_callback
   return 0;
 }
 
-int on_invalid_frame_recv_callback
+int verbose_on_invalid_frame_recv_callback
 (nghttp2_session *session, const nghttp2_frame *frame,
  nghttp2_error_code error_code, void *user_data)
 {
@@ -374,13 +374,14 @@ void dump_header(const uint8_t *head, size_t headlen)
 }
 } // namespace
 
-int on_frame_recv_parse_error_callback(nghttp2_session *session,
-                                       nghttp2_frame_type type,
-                                       const uint8_t *head,
-                                       size_t headlen,
-                                       const uint8_t *payload,
-                                       size_t payloadlen,
-                                       int error_code, void *user_data)
+int verbose_on_frame_recv_parse_error_callback(nghttp2_session *session,
+                                               nghttp2_frame_type type,
+                                               const uint8_t *head,
+                                               size_t headlen,
+                                               const uint8_t *payload,
+                                               size_t payloadlen,
+                                               int error_code,
+                                               void *user_data)
 {
   print_timer();
   printf(" [PARSE_ERROR] recv %s%s%s frame\n",
@@ -394,12 +395,12 @@ int on_frame_recv_parse_error_callback(nghttp2_session *session,
   return 0;
 }
 
-int on_unknown_frame_recv_callback(nghttp2_session *session,
-                                   const uint8_t *head,
-                                   size_t headlen,
-                                   const uint8_t *payload,
-                                   size_t payloadlen,
-                                   void *user_data)
+int verbose_on_unknown_frame_recv_callback(nghttp2_session *session,
+                                           const uint8_t *head,
+                                           size_t headlen,
+                                           const uint8_t *payload,
+                                           size_t payloadlen,
+                                           void *user_data)
 {
   print_timer();
   printf(" recv unknown frame\n");
@@ -408,7 +409,7 @@ int on_unknown_frame_recv_callback(nghttp2_session *session,
   return 0;
 }
 
-int on_frame_send_callback
+int verbose_on_frame_send_callback
 (nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
 {
   print_timer();
@@ -433,7 +434,7 @@ void print_data_frame(print_type ptype, uint16_t length, uint8_t flags,
 }
 } // namespace
 
-int on_data_recv_callback
+int verbose_on_data_recv_callback
 (nghttp2_session *session, uint16_t length, uint8_t flags, int32_t stream_id,
  void *user_data)
 {
@@ -444,7 +445,7 @@ int on_data_recv_callback
   return 0;
 }
 
-int on_data_send_callback
+int verbose_on_data_send_callback
 (nghttp2_session *session, uint16_t length, uint8_t flags, int32_t stream_id,
  void *user_data)
 {
diff --git a/src/app_helper.h b/src/app_helper.h
index aaf1b6fb..c66e53e4 100644
--- a/src/app_helper.h
+++ b/src/app_helper.h
@@ -41,36 +41,37 @@ namespace nghttp2 {
 
 void print_nv(char **nv);
 
-int on_frame_recv_callback
+int verbose_on_frame_recv_callback
 (nghttp2_session *session, const nghttp2_frame *frame, void *user_data);
 
-int on_invalid_frame_recv_callback
+int verbose_on_invalid_frame_recv_callback
 (nghttp2_session *session, const nghttp2_frame *frame,
  nghttp2_error_code error_code, void *user_data);
 
-int on_frame_recv_parse_error_callback(nghttp2_session *session,
-                                       nghttp2_frame_type type,
-                                       const uint8_t *head,
-                                       size_t headlen,
-                                       const uint8_t *payload,
-                                       size_t payloadlen,
-                                       int error_code, void *user_data);
+int verbose_on_frame_recv_parse_error_callback(nghttp2_session *session,
+                                               nghttp2_frame_type type,
+                                               const uint8_t *head,
+                                               size_t headlen,
+                                               const uint8_t *payload,
+                                               size_t payloadlen,
+                                               int error_code,
+                                               void *user_data);
 
-int on_unknown_frame_recv_callback(nghttp2_session *session,
-                                   const uint8_t *head,
-                                   size_t headlen,
-                                   const uint8_t *payload,
-                                   size_t payloadlen,
-                                   void *user_data);
+int verbose_on_unknown_frame_recv_callback(nghttp2_session *session,
+                                           const uint8_t *head,
+                                           size_t headlen,
+                                           const uint8_t *payload,
+                                           size_t payloadlen,
+                                           void *user_data);
 
-int on_frame_send_callback
+int verbose_on_frame_send_callback
 (nghttp2_session *session, const nghttp2_frame *frame, void *user_data);
 
-int on_data_recv_callback
+int verbose_on_data_recv_callback
 (nghttp2_session *session, uint16_t length, uint8_t flags, int32_t stream_id,
  void *user_data);
 
-int on_data_send_callback
+int verbose_on_data_send_callback
 (nghttp2_session *session, uint16_t length, uint8_t flags, int32_t stream_id,
  void *user_data);
 
diff --git a/src/nghttp.cc b/src/nghttp.cc
index bdaf9e3b..1f43ba53 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -1096,17 +1096,6 @@ int before_frame_send_callback
 }
 } // namespace
 
-namespace {
-int on_frame_send_callback2
-(nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
-{
-  if(config.verbose) {
-    on_frame_send_callback(session, frame, user_data);
-  }
-  return 0;
-}
-} // namespace
-
 namespace {
 void check_response_header
 (nghttp2_session *session, const nghttp2_frame *frame, void *user_data)
@@ -1169,7 +1158,7 @@ int on_frame_recv_callback2
     }
   }
   if(config.verbose) {
-    on_frame_recv_callback(session, frame, user_data);
+    verbose_on_frame_recv_callback(session, frame, user_data);
   }
   return 0;
 }
@@ -1480,15 +1469,17 @@ int run(char **uris, int n)
   callbacks.recv_callback = client_recv_callback;
   callbacks.on_stream_close_callback = on_stream_close_callback;
   callbacks.on_frame_recv_callback = on_frame_recv_callback2;
-  callbacks.on_frame_send_callback = on_frame_send_callback2;
   callbacks.before_frame_send_callback = before_frame_send_callback;
   if(config.verbose) {
-    callbacks.on_data_recv_callback = on_data_recv_callback;
-    callbacks.on_data_send_callback = on_data_send_callback;
-    callbacks.on_invalid_frame_recv_callback = on_invalid_frame_recv_callback;
+    callbacks.on_frame_send_callback = verbose_on_frame_send_callback;
+    callbacks.on_data_recv_callback = verbose_on_data_recv_callback;
+    callbacks.on_data_send_callback = verbose_on_data_send_callback;
+    callbacks.on_invalid_frame_recv_callback =
+      verbose_on_invalid_frame_recv_callback;
     callbacks.on_frame_recv_parse_error_callback =
-      on_frame_recv_parse_error_callback;
-    callbacks.on_unknown_frame_recv_callback = on_unknown_frame_recv_callback;
+      verbose_on_frame_recv_parse_error_callback;
+    callbacks.on_unknown_frame_recv_callback =
+      verbose_on_unknown_frame_recv_callback;
   }
   callbacks.on_data_chunk_recv_callback = on_data_chunk_recv_callback;
   std::string prev_scheme;