diff --git a/src/shrpx_exec.cc b/src/shrpx_exec.cc
index efff4d68..d5cd0916 100644
--- a/src/shrpx_exec.cc
+++ b/src/shrpx_exec.cc
@@ -84,7 +84,7 @@ int exec_read_command(Process &proc, char *const argv[]) {
 
     rv = shrpx_signal_unblock_all();
     if (rv != 0) {
-      constexpr char msg[] = "Unblocking all signals failed\n";
+      static constexpr char msg[] = "Unblocking all signals failed\n";
       while (write(STDERR_FILENO, msg, str_size(msg)) == -1 && errno == EINTR)
         ;
       nghttp2_Exit(EXIT_FAILURE);
@@ -95,7 +95,7 @@ int exec_read_command(Process &proc, char *const argv[]) {
 
     rv = execv(argv[0], argv);
     if (rv == -1) {
-      constexpr char msg[] = "Could not execute command\n";
+      static constexpr char msg[] = "Could not execute command\n";
       while (write(STDERR_FILENO, msg, str_size(msg)) == -1 && errno == EINTR)
         ;
       nghttp2_Exit(EXIT_FAILURE);
diff --git a/src/shrpx_tls_test.cc b/src/shrpx_tls_test.cc
index 7445c151..b227dda5 100644
--- a/src/shrpx_tls_test.cc
+++ b/src/shrpx_tls_test.cc
@@ -70,7 +70,7 @@ void test_shrpx_tls_create_lookup_tree(void) {
   CU_ASSERT(-1 == tree->lookup(StringRef{}));
   CU_ASSERT(5 == tree->lookup(hostnames[5]));
   CU_ASSERT(6 == tree->lookup(hostnames[6]));
-  constexpr char h6[] = "pdylay.sourceforge.net";
+  static constexpr char h6[] = "pdylay.sourceforge.net";
   for (int i = 0; i < 7; ++i) {
     CU_ASSERT(-1 == tree->lookup(StringRef{h6 + i, str_size(h6) - i}));
   }
@@ -119,7 +119,8 @@ void test_shrpx_tls_create_lookup_tree(void) {
 void test_shrpx_tls_cert_lookup_tree_add_ssl_ctx(void) {
   int rv;
 
-  constexpr char nghttp2_certfile[] = NGHTTP2_SRC_DIR "/test.nghttp2.org.pem";
+  static constexpr char nghttp2_certfile[] =
+      NGHTTP2_SRC_DIR "/test.nghttp2.org.pem";
   auto nghttp2_ssl_ctx = SSL_CTX_new(SSLv23_server_method());
   auto nghttp2_ssl_ctx_del = defer(SSL_CTX_free, nghttp2_ssl_ctx);
   auto nghttp2_tls_ctx_data = make_unique<tls::TLSContextData>();
@@ -129,7 +130,8 @@ void test_shrpx_tls_cert_lookup_tree_add_ssl_ctx(void) {
 
   CU_ASSERT(1 == rv);
 
-  constexpr char examples_certfile[] = NGHTTP2_SRC_DIR "/test.example.com.pem";
+  static constexpr char examples_certfile[] =
+      NGHTTP2_SRC_DIR "/test.example.com.pem";
   auto examples_ssl_ctx = SSL_CTX_new(SSLv23_server_method());
   auto examples_ssl_ctx_del = defer(SSL_CTX_free, examples_ssl_ctx);
   auto examples_tls_ctx_data = make_unique<tls::TLSContextData>();
diff --git a/src/util.h b/src/util.h
index 49d0c4b1..af70a2a4 100644
--- a/src/util.h
+++ b/src/util.h
@@ -716,7 +716,7 @@ template <typename OutputIt, typename Generator>
 OutputIt random_alpha_digit(OutputIt first, OutputIt last, Generator &gen) {
   // If we use uint8_t instead char, gcc 6.2.0 complains by shouting
   // char-array initialized from wide string.
-  constexpr char s[] =
+  static constexpr char s[] =
       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
   std::uniform_int_distribution<> dis(0, 26 * 2 + 10 - 1);
   for (; first != last; ++first) {