diff --git a/src/shrpx.cc b/src/shrpx.cc
index ac982137..1b5db457 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -545,17 +545,27 @@ void print_help(std::ostream& out)
       << "    --backend-no-tls   Disable SSL/TLS on backend connections.\n"
       << "\n"
       << "  Mode:\n"
-      << "    -s, --spdy-proxy   Enable secure HTTP/2.0 and SPDY proxy mode.\n"
-      << "    --spdy-bridge      Communicate with the backend in HTTP/2.0. Thus\n"
-      << "                       the incoming all connections are\n"
-      << "                       converted to HTTP/2.0 connection and relayed to\n"
+      << "    (default mode)     Accept HTTP/2.0, SPDY and HTTP/1.1 over\n"
+      << "                       SSL/TLS. If --frontend-no-tls is used,\n"
+      << "                       accept HTTP/2.0 and HTTP/1.1. The incoming\n"
+      << "                       HTTP/1.1 connection can be upgraded to\n"
+      << "                       HTTP/2.0 through HTTP Upgrade.\n"
+      << "                       The protocol to the backend is HTTP/1.1.\n"
+      << "    -s, --spdy-proxy   Like default mode, but enable secure proxy mode.\n"
+      << "    --spdy-bridge      Like default mode, but communicate with the\n"
+      << "                       backend in HTTP/2.0 over SSL/TLS. Thus the\n"
+      << "                       incoming all connections are converted\n"
+      << "                       to HTTP/2.0 connection and relayed to\n"
       << "                       the backend. See --backend-http-proxy-uri\n"
       << "                       option if you are behind the proxy and want\n"
       << "                       to connect to the outside HTTP/2.0 proxy.\n"
-      << "    --client           Instead of accepting HTTP/2.0, SPDY/HTTPS connection,\n"
-      << "                       accept plain HTTP/1.1 connection and communicate with\n"
-      << "                       backend server in HTTP/2.0. To use nghttpx as\n"
-      << "                       a forward proxy, use -p option instead.\n"
+      << "    --client           Accept HTTP/2.0 and HTTP/1.1 without SSL/TLS.\n"
+      << "                       The incoming HTTP/1.1 connection can be\n"
+      << "                       upgraded to HTTP/2.0 connection through\n"
+      << "                       HTTP Upgrade.\n"
+      << "                       The protocol to the backend is HTTP/2.0.\n"
+      << "                       To use nghttpx as a forward proxy, use -p\n"
+      << "                       option instead.\n"
       << "    -p, --client-proxy Like --client option, but it also requires\n"
       << "                       the request path from frontend must be\n"
       << "                       an absolute URI, suitable for use as a\n"