diff --git a/src/shrpx.cc b/src/shrpx.cc
index 677974da..d3374ea2 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -2448,8 +2448,7 @@ int process_options(Config *config,
     tlsconf.npn_list = util::split_str(DEFAULT_NPN_LIST, ',');
   }
   if (tlsconf.tls_proto_list.empty()) {
-    tlsconf.tls_proto_list =
-        util::parse_config_str_list(DEFAULT_TLS_PROTO_LIST);
+    tlsconf.tls_proto_list = util::split_str(DEFAULT_TLS_PROTO_LIST, ',');
   }
 
   tlsconf.tls_proto_mask = ssl::create_tls_proto_mask(tlsconf.tls_proto_list);
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 066aa731..6ed55919 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -2309,7 +2309,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_TLS_PROTO_LIST:
-    config->tls.tls_proto_list = util::parse_config_str_list(optarg);
+    config->tls.tls_proto_list = util::split_str(optarg, ',');
 
     return 0;
   case SHRPX_OPTID_VERIFY_CLIENT:
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index b3c98ed8..ff55a2a0 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -528,7 +528,7 @@ struct TLSConfig {
   // preference.
   std::vector<StringRef> npn_list;
   // list of supported SSL/TLS protocol strings.
-  std::vector<std::string> tls_proto_list;
+  std::vector<StringRef> tls_proto_list;
   BIO_METHOD *bio_method;
   // Bit mask to disable SSL/TLS protocol versions.  This will be
   // passed to SSL_CTX_set_options().
diff --git a/src/shrpx_ssl.cc b/src/shrpx_ssl.cc
index a53dbe62..6eb243aa 100644
--- a/src/shrpx_ssl.cc
+++ b/src/shrpx_ssl.cc
@@ -495,7 +495,7 @@ constexpr TLSProtocol TLS_PROTOS[] = {
     TLSProtocol{StringRef::from_lit("TLSv1.1"), SSL_OP_NO_TLSv1_1},
     TLSProtocol{StringRef::from_lit("TLSv1.0"), SSL_OP_NO_TLSv1}};
 
-long int create_tls_proto_mask(const std::vector<std::string> &tls_proto_list) {
+long int create_tls_proto_mask(const std::vector<StringRef> &tls_proto_list) {
   long int res = 0;
 
   for (auto &supported : TLS_PROTOS) {
diff --git a/src/shrpx_ssl.h b/src/shrpx_ssl.h
index 010072a6..d7f4f8b1 100644
--- a/src/shrpx_ssl.h
+++ b/src/shrpx_ssl.h
@@ -176,7 +176,7 @@ bool check_http2_requirement(SSL *ssl);
 // Returns SSL/TLS option mask to disable SSL/TLS protocol version not
 // included in |tls_proto_list|.  The returned mask can be directly
 // passed to SSL_CTX_set_options().
-long int create_tls_proto_mask(const std::vector<std::string> &tls_proto_list);
+long int create_tls_proto_mask(const std::vector<StringRef> &tls_proto_list);
 
 int set_alpn_prefs(std::vector<unsigned char> &out,
                    const std::vector<StringRef> &protos);