diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 90bdc1c2..9c5d9917 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -304,7 +304,7 @@ read_quic_secret_file(const StringRef &path) {
 FILE *open_file_for_write(const char *filename) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
 
-#if defined O_CLOEXEC
+#ifdef O_CLOEXEC
   auto fd = open(filename, O_WRONLY | O_CLOEXEC | O_CREAT | O_TRUNC,
                  S_IRUSR | S_IWUSR);
 #else
diff --git a/src/shrpx_connection.cc b/src/shrpx_connection.cc
index 229e693c..af3cc05a 100644
--- a/src/shrpx_connection.cc
+++ b/src/shrpx_connection.cc
@@ -503,9 +503,9 @@ int Connection::tls_handshake() {
   // routine.  We have to check HTTP/2 requirement if HTTP/2 was
   // negotiated before sending finished message to the peer.
   if ((rv != 1
-#if defined(OPENSSL_IS_BORINGSSL)
+#ifdef OPENSSL_IS_BORINGSSL
        || SSL_in_init(tls.ssl)
-#endif // defined(OPENSSL_IS_BORINGSSL)
+#endif // OPENSSL_IS_BORINGSSL
            ) &&
       tls.wbuf.rleft()) {
     // First write indicates that resumption stuff has done.
@@ -543,7 +543,7 @@ int Connection::tls_handshake() {
     return SHRPX_ERR_INPROGRESS;
   }
 
-#if defined(OPENSSL_IS_BORINGSSL)
+#ifdef OPENSSL_IS_BORINGSSL
   if (!tlsconf.no_postpone_early_data && SSL_in_early_data(tls.ssl) &&
       SSL_in_init(tls.ssl)) {
     auto nread = SSL_read(tls.ssl, buf.data(), buf.size());
@@ -575,7 +575,7 @@ int Connection::tls_handshake() {
       return SHRPX_ERR_INPROGRESS;
     }
   }
-#endif // defined(OPENSSL_IS_BORINGSSL)
+#endif // OPENSSL_IS_BORINGSSL
 
   // Handshake was done
 
@@ -613,7 +613,7 @@ int Connection::write_tls_pending_handshake() {
     tls.wbuf.drain(nwrite);
   }
 
-#if defined(OPENSSL_IS_BORINGSSL)
+#ifdef OPENSSL_IS_BORINGSSL
   if (!SSL_in_init(tls.ssl)) {
     // This will send a session ticket.
     auto nwrite = SSL_write(tls.ssl, "", 0);
@@ -641,7 +641,7 @@ int Connection::write_tls_pending_handshake() {
       }
     }
   }
-#endif // defined(OPENSSL_IS_BORINGSSL)
+#endif // OPENSSL_IS_BORINGSSL
 
   // We have to start read watcher, since later stage of code expects
   // this.
diff --git a/src/shrpx_log.cc b/src/shrpx_log.cc
index 8fd8b11c..3a5af823 100644
--- a/src/shrpx_log.cc
+++ b/src/shrpx_log.cc
@@ -964,7 +964,7 @@ int open_log_file(const char *path) {
       strcmp(path, "/proc/self/fd/2") == 0) {
     return STDERR_COPY;
   }
-#if defined O_CLOEXEC
+#ifdef O_CLOEXEC
 
   auto fd = open(path, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC,
                  S_IRUSR | S_IWUSR | S_IRGRP);
diff --git a/src/shrpx_tls.cc b/src/shrpx_tls.cc
index 12539ad5..bb0017e6 100644
--- a/src/shrpx_tls.cc
+++ b/src/shrpx_tls.cc
@@ -2648,7 +2648,7 @@ int time_t_from_asn1_time(time_t &t, const ASN1_TIME *at) {
     return -1;
   }
 
-#  if defined(OPENSSL_IS_BORINGSSL)
+#  ifdef OPENSSL_IS_BORINGSSL
   char *s;
 #  else
   unsigned char *s;
diff --git a/src/ssl_compat.h b/src/ssl_compat.h
index e1077eef..87f326a4 100644
--- a/src/ssl_compat.h
+++ b/src/ssl_compat.h
@@ -26,20 +26,20 @@
 
 #  include <openssl/opensslv.h>
 
-#  if defined(LIBRESSL_VERSION_NUMBER)
+#  ifdef LIBRESSL_VERSION_NUMBER
 #    define OPENSSL_1_1_API 0
 #    define OPENSSL_1_1_1_API 0
 #    define OPENSSL_3_0_0_API 0
 #    define LIBRESSL_IN_USE 1
 #    define LIBRESSL_LEGACY_API (LIBRESSL_VERSION_NUMBER < 0x20700000L)
 #    define LIBRESSL_2_7_API (LIBRESSL_VERSION_NUMBER >= 0x20700000L)
-#  else // !defined(LIBRESSL_VERSION_NUMBER)
+#  else // !LIBRESSL_VERSION_NUMBER
 #    define OPENSSL_1_1_API (OPENSSL_VERSION_NUMBER >= 0x1010000fL)
 #    define OPENSSL_1_1_1_API (OPENSSL_VERSION_NUMBER >= 0x10101000L)
 #    define OPENSSL_3_0_0_API (OPENSSL_VERSION_NUMBER >= 0x30000000L)
 #    define LIBRESSL_IN_USE 0
 #    define LIBRESSL_LEGACY_API 0
 #    define LIBRESSL_2_7_API 0
-#  endif // !defined(LIBRESSL_VERSION_NUMBER)
+#  endif // !LIBRESSL_VERSION_NUMBER
 
 #endif // OPENSSL_COMPAT_H
diff --git a/src/util.cc b/src/util.cc
index 4db6325d..213989e4 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -1649,7 +1649,7 @@ std::mt19937 make_mt19937() {
 }
 
 int daemonize(int nochdir, int noclose) {
-#if defined(__APPLE__)
+#ifdef __APPLE__
   pid_t pid;
   pid = fork();
   if (pid == -1) {
@@ -1683,9 +1683,9 @@ int daemonize(int nochdir, int noclose) {
     }
   }
   return 0;
-#else  // !defined(__APPLE__)
+#else  // !__APPLE__
   return daemon(nochdir, noclose);
-#endif // !defined(__APPLE__)
+#endif // !__APPLE__
 }
 
 #ifdef ENABLE_HTTP3