diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index d32d128e..0bace4d6 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -418,8 +418,10 @@ int Http2Handler::read_clear() {
     }
     rv = nghttp2_session_mem_recv(session_, buf, nread);
     if (rv < 0) {
-      std::cerr << "nghttp2_session_mem_recv() returned error: "
-                << nghttp2_strerror(rv) << std::endl;
+      if (rv != NGHTTP2_ERR_BAD_PREFACE) {
+        std::cerr << "nghttp2_session_mem_recv() returned error: "
+                  << nghttp2_strerror(rv) << std::endl;
+      }
       return -1;
     }
   }
@@ -540,8 +542,10 @@ int Http2Handler::read_tls() {
     auto nread = rv;
     rv = nghttp2_session_mem_recv(session_, buf, nread);
     if (rv < 0) {
-      std::cerr << "nghttp2_session_mem_recv() returned error: "
-                << nghttp2_strerror(rv) << std::endl;
+      if (rv != NGHTTP2_ERR_BAD_PREFACE) {
+        std::cerr << "nghttp2_session_mem_recv() returned error: "
+                  << nghttp2_strerror(rv) << std::endl;
+      }
       return -1;
     }
   }
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index f2b47bf3..033580ec 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -780,8 +780,10 @@ int Http2Upstream::on_read() {
   if (rb->rleft()) {
     rv = nghttp2_session_mem_recv(session_, rb->pos, rb->rleft());
     if (rv < 0) {
-      ULOG(ERROR, this) << "nghttp2_session_recv() returned error: "
-                        << nghttp2_strerror(rv);
+      if (rv != NGHTTP2_ERR_BAD_PREFACE) {
+        ULOG(ERROR, this) << "nghttp2_session_recv() returned error: "
+                          << nghttp2_strerror(rv);
+      }
       return -1;
     }