diff --git a/src/h2load.cc b/src/h2load.cc
index 74cbcaf7..6ce7b023 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -77,6 +77,7 @@ bool recorded(const std::chrono::steady_clock::time_point &t) {
 
 Config::Config()
     : ciphers(tls::DEFAULT_CIPHER_LIST),
+      groups("P-256:X25519:P-384:P-521"),
       data_length(-1),
       addrs(nullptr),
       nreqs(1),
@@ -2220,6 +2221,10 @@ Options:
               in <URI>.
   --rps=<N>   Specify request  per second for each  client.  --rps and
               --timing-script-file are mutually exclusive.
+  --groups=<GROUPS>
+              Specify the supported groups.
+              Default: )"
+      << config.groups << R"(
   -v, --verbose
               Output debug information.
   --version   Display version information and exit.
@@ -2280,6 +2285,7 @@ int main(int argc, char **argv) {
         {"log-file", required_argument, &flag, 10},
         {"connect-to", required_argument, &flag, 11},
         {"rps", required_argument, &flag, 12},
+        {"groups", required_argument, &flag, 13},
         {nullptr, 0, nullptr, 0}};
     int option_index = 0;
     auto c = getopt_long(argc, argv,
@@ -2530,6 +2536,10 @@ int main(int argc, char **argv) {
         config.rps = v;
         break;
       }
+      case 13:
+        // --groups
+        config.groups = optarg;
+        break;
       }
       break;
     default:
@@ -2758,7 +2768,11 @@ int main(int argc, char **argv) {
   }
 
   // TODO Use SSL_CTX_set_ciphersuites to set TLSv1.3 cipher list
-  // TODO Use SSL_CTX_set1_groups_list to set key share
+
+  if (SSL_CTX_set1_groups_list(ssl_ctx, config.groups.c_str()) != 1) {
+    std::cerr << "SSL_CTX_set1_groups_list failed" << std::endl;
+    exit(EXIT_FAILURE);
+  }
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, client_select_next_proto_cb,
diff --git a/src/h2load.h b/src/h2load.h
index 1225318a..9b25ce93 100644
--- a/src/h2load.h
+++ b/src/h2load.h
@@ -75,6 +75,8 @@ struct Config {
   std::string connect_to_host;
   std::string ifile;
   std::string ciphers;
+  // supported groups (or curves).
+  std::string groups;
   // length of upload data
   int64_t data_length;
   addrinfo *addrs;