diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index 74fd42fb..291e25e6 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -711,6 +711,9 @@ struct QUICConfig {
   struct {
     ev_tstamp idle;
   } timeout;
+  struct {
+    bool log;
+  } debug;
 };
 
 // custom error page
diff --git a/src/shrpx_http3_upstream.cc b/src/shrpx_http3_upstream.cc
index 5c05fe0d..e4b945ae 100644
--- a/src/shrpx_http3_upstream.cc
+++ b/src/shrpx_http3_upstream.cc
@@ -451,9 +451,14 @@ int Http3Upstream::init(const UpstreamAddr *faddr, const Address &remote_addr,
     return -1;
   }
 
+  auto config = get_config();
+  auto &quicconf = config->quic;
+
   ngtcp2_settings settings;
   ngtcp2_settings_default(&settings);
-  settings.log_printf = log_printf;
+  if (quicconf.debug.log) {
+    settings.log_printf = log_printf;
+  }
   settings.initial_ts = quic_timestamp();
   settings.cc_algo = NGTCP2_CC_ALGO_BBR;
   settings.max_window = 6_m;
@@ -461,9 +466,6 @@ int Http3Upstream::init(const UpstreamAddr *faddr, const Address &remote_addr,
   settings.max_udp_payload_size = SHRPX_MAX_UDP_PAYLOAD_SIZE;
   settings.rand_ctx.native_handle = &worker->get_randgen();
 
-  auto config = get_config();
-  auto &quicconf = config->quic;
-
   ngtcp2_transport_params params;
   ngtcp2_transport_params_default(&params);
   params.initial_max_streams_bidi = 100;