diff --git a/src/nghttp.cc b/src/nghttp.cc
index 26e7ec3e..379484ad 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -1462,23 +1462,23 @@ int main(int argc, char **argv)
   while(1) {
     int flag;
     static option long_options[] = {
-      {"verbose", no_argument, 0, 'v' },
-      {"null-out", no_argument, 0, 'n' },
-      {"remote-name", no_argument, 0, 'O' },
-      {"timeout", required_argument, 0, 't' },
-      {"window-bits", required_argument, 0, 'w' },
-      {"get-assets", no_argument, 0, 'a' },
-      {"stat", no_argument, 0, 's' },
-      {"cert", required_argument, &flag, 1 },
-      {"key", required_argument, &flag, 2 },
-      {"help", no_argument, 0, 'h' },
-      {"header", required_argument, 0, 'H' },
-      {"data", required_argument, 0, 'd' },
-      {"multiply", required_argument, 0, 'm' },
-      {"no-flow-control", no_argument, 0, 'f'},
-      {"upgrade", no_argument, 0, 'u'},
-      {"pri", required_argument, 0, 'p'},
-      {0, 0, 0, 0 }
+      {"verbose", no_argument, nullptr, 'v'},
+      {"null-out", no_argument, nullptr, 'n'},
+      {"remote-name", no_argument, nullptr, 'O'},
+      {"timeout", required_argument, nullptr, 't'},
+      {"window-bits", required_argument, nullptr, 'w'},
+      {"get-assets", no_argument, nullptr, 'a'},
+      {"stat", no_argument, nullptr, 's'},
+      {"cert", required_argument, &flag, 1},
+      {"key", required_argument, &flag, 2},
+      {"help", no_argument, nullptr, 'h'},
+      {"header", required_argument, nullptr, 'H'},
+      {"data", required_argument, nullptr, 'd'},
+      {"multiply", required_argument, nullptr, 'm'},
+      {"no-flow-control", no_argument, nullptr, 'f'},
+      {"upgrade", no_argument, nullptr, 'u'},
+      {"pri", required_argument, nullptr, 'p'},
+      {nullptr, 0, nullptr, 0 }
     };
     int option_index = 0;
     int c = getopt_long(argc, argv, "Oad:fm:np:hH:vst:uw:", long_options,
diff --git a/src/nghttpd.cc b/src/nghttpd.cc
index ca534c15..c001540d 100644
--- a/src/nghttpd.cc
+++ b/src/nghttpd.cc
@@ -87,14 +87,14 @@ int main(int argc, char **argv)
   while(1) {
     int flag;
     static option long_options[] = {
-      {"daemon", no_argument, 0, 'D' },
-      {"htdocs", required_argument, 0, 'd' },
-      {"help", no_argument, 0, 'h' },
-      {"verbose", no_argument, 0, 'v' },
-      {"verify-client", no_argument, 0, 'V' },
-      {"no-tls", no_argument, &flag, 1 },
-      {"no-flow-control", no_argument, 0, 'f'},
-      {0, 0, 0, 0 }
+      {"daemon", no_argument, nullptr, 'D'},
+      {"htdocs", required_argument, nullptr, 'd'},
+      {"help", no_argument, nullptr, 'h'},
+      {"verbose", no_argument, nullptr, 'v'},
+      {"verify-client", no_argument, nullptr, 'V'},
+      {"no-tls", no_argument, &flag, 1},
+      {"no-flow-control", no_argument, nullptr, 'f'},
+      {nullptr, 0, nullptr, 0}
     };
     int option_index = 0;
     int c = getopt_long(argc, argv, "DVd:fhv", long_options, &option_index);
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 6643bf42..0ae70e92 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -619,38 +619,38 @@ int main(int argc, char **argv)
   while(1) {
     int flag;
     static option long_options[] = {
-      {"daemon", no_argument, 0, 'D' },
-      {"log-level", required_argument, 0, 'L' },
-      {"backend", required_argument, 0, 'b' },
-      {"spdy-max-concurrent-streams", required_argument, 0, 'c' },
-      {"frontend", required_argument, 0, 'f' },
-      {"help", no_argument, 0, 'h' },
-      {"insecure", no_argument, 0, 'k' },
-      {"workers", required_argument, 0, 'n' },
-      {"client-proxy", no_argument, 0, 'p' },
-      {"spdy-proxy", no_argument, 0, 's' },
-      {"version", no_argument, 0, 'v' },
-      {"add-x-forwarded-for", no_argument, &flag, 1 },
-      {"frontend-spdy-read-timeout", required_argument, &flag, 2 },
-      {"frontend-read-timeout", required_argument, &flag, 3 },
-      {"frontend-write-timeout", required_argument, &flag, 4 },
-      {"backend-read-timeout", required_argument, &flag, 5 },
-      {"backend-write-timeout", required_argument, &flag, 6 },
-      {"accesslog", no_argument, &flag, 7 },
-      {"backend-keep-alive-timeout", required_argument, &flag, 8 },
-      {"frontend-spdy-window-bits", required_argument, &flag, 9 },
-      {"pid-file", required_argument, &flag, 10 },
-      {"user", required_argument, &flag, 11 },
-      {"conf", required_argument, &flag, 12 },
-      {"syslog", no_argument, &flag, 13 },
-      {"syslog-facility", required_argument, &flag, 14 },
-      {"backlog", required_argument, &flag, 15 },
-      {"ciphers", required_argument, &flag, 16 },
-      {"client", no_argument, &flag, 17 },
-      {"backend-spdy-window-bits", required_argument, &flag, 18 },
-      {"cacert", required_argument, &flag, 19 },
-      {"backend-ipv4", no_argument, &flag, 20 },
-      {"backend-ipv6", no_argument, &flag, 21 },
+      {"daemon", no_argument, nullptr, 'D'},
+      {"log-level", required_argument, nullptr, 'L'},
+      {"backend", required_argument, nullptr, 'b'},
+      {"spdy-max-concurrent-streams", required_argument, nullptr, 'c'},
+      {"frontend", required_argument, nullptr, 'f'},
+      {"help", no_argument, nullptr, 'h'},
+      {"insecure", no_argument, nullptr, 'k'},
+      {"workers", required_argument, nullptr, 'n'},
+      {"client-proxy", no_argument, nullptr, 'p'},
+      {"spdy-proxy", no_argument, nullptr, 's'},
+      {"version", no_argument, nullptr, 'v'},
+      {"add-x-forwarded-for", no_argument, &flag, 1},
+      {"frontend-spdy-read-timeout", required_argument, &flag, 2},
+      {"frontend-read-timeout", required_argument, &flag, 3},
+      {"frontend-write-timeout", required_argument, &flag, 4},
+      {"backend-read-timeout", required_argument, &flag, 5},
+      {"backend-write-timeout", required_argument, &flag, 6},
+      {"accesslog", no_argument, &flag, 7},
+      {"backend-keep-alive-timeout", required_argument, &flag, 8},
+      {"frontend-spdy-window-bits", required_argument, &flag, 9},
+      {"pid-file", required_argument, &flag, 10},
+      {"user", required_argument, &flag, 11},
+      {"conf", required_argument, &flag, 12},
+      {"syslog", no_argument, &flag, 13},
+      {"syslog-facility", required_argument, &flag, 14},
+      {"backlog", required_argument, &flag, 15},
+      {"ciphers", required_argument, &flag, 16},
+      {"client", no_argument, &flag, 17},
+      {"backend-spdy-window-bits", required_argument, &flag, 18},
+      {"cacert", required_argument, &flag, 19},
+      {"backend-ipv4", no_argument, &flag, 20},
+      {"backend-ipv6", no_argument, &flag, 21},
       {"private-key-passwd-file", required_argument, &flag, 22},
       {"no-via", no_argument, &flag, 23},
       {"subcert", required_argument, &flag, 24},
@@ -660,7 +660,7 @@ int main(int argc, char **argv)
       {"frontend-no-tls", no_argument, &flag, 29},
       {"backend-tls-sni-field", required_argument, &flag, 31},
       {"honor-cipher-order", no_argument, &flag, 32},
-      {0, 0, 0, 0 }
+      {nullptr, 0, nullptr, 0 }
     };
     int option_index = 0;
     int c = getopt_long(argc, argv, "DL:b:c:f:hkn:psv", long_options,