diff --git a/example/sftpdir.c b/example/sftpdir.c
index 815b452a..85b3947f 100644
--- a/example/sftpdir.c
+++ b/example/sftpdir.c
@@ -30,7 +30,7 @@
 #include <stdio.h>
 #include <string.h>
 
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 #define LIBSSH2_FILESIZE_MASK "I64u"
 #else
 #define LIBSSH2_FILESIZE_MASK "llu"
diff --git a/example/sftpdir_nonblock.c b/example/sftpdir_nonblock.c
index 59b178c8..0e31a8d4 100644
--- a/example/sftpdir_nonblock.c
+++ b/example/sftpdir_nonblock.c
@@ -29,7 +29,7 @@
 
 #include <stdio.h>
 
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 #define LIBSSH2_FILESIZE_MASK "I64u"
 #else
 #define LIBSSH2_FILESIZE_MASK "llu"
diff --git a/example/x11.c b/example/x11.c
index 285cd611..8b83be32 100644
--- a/example/x11.c
+++ b/example/x11.c
@@ -347,13 +347,13 @@ int main(int argc, char *argv[])
         libssh2_trace(session, LIBSSH2_TRACE_CONN);
 
     /* Set X11 Callback */
-#if defined(__clang__)
+#ifdef __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wcast-function-type"
 #endif
     libssh2_session_callback_set2(session, LIBSSH2_CALLBACK_X11,
                                   (libssh2_cb_generic *)x11_callback);
-#if defined(__clang__)
+#ifdef __clang__
 #pragma clang diagnostic pop
 #endif
 
diff --git a/src/libssh2_priv.h b/src/libssh2_priv.h
index cb153a89..ff40bcfb 100644
--- a/src/libssh2_priv.h
+++ b/src/libssh2_priv.h
@@ -141,7 +141,7 @@
 #endif
 
 /* Use local implementation when not available */
-#if !defined(HAVE_SNPRINTF)
+#ifndef HAVE_SNPRINTF
 #undef snprintf
 #define snprintf _libssh2_snprintf
 #define LIBSSH2_SNPRINTF
@@ -149,7 +149,7 @@ int _libssh2_snprintf(char *cp, size_t cp_max_len, const char *fmt, ...)
     LIBSSH2_PRINTF(3, 4);
 #endif
 
-#if !defined(HAVE_GETTIMEOFDAY)
+#ifndef HAVE_GETTIMEOFDAY
 #define HAVE_GETTIMEOFDAY
 #undef gettimeofday
 #define gettimeofday _libssh2_gettimeofday
@@ -159,7 +159,7 @@ int _libssh2_gettimeofday(struct timeval *tp, void *tzp);
 #include <sys/time.h>
 #endif
 
-#if !defined(LIBSSH2_FALLTHROUGH)
+#ifndef LIBSSH2_FALLTHROUGH
 #if (defined(__GNUC__) && __GNUC__ >= 7) || \
     (defined(__clang__) && __clang_major__ >= 10)
 #  define LIBSSH2_FALLTHROUGH()  __attribute__((fallthrough))
diff --git a/src/mbedtls.h b/src/mbedtls.h
index dfc34821..05d26b5c 100644
--- a/src/mbedtls.h
+++ b/src/mbedtls.h
@@ -48,7 +48,7 @@
 #if !defined(__clang__) && __GNUC__ >= 10
 #pragma GCC diagnostic ignored "-Warith-conversion"
 #endif
-#if defined(__clang__)
+#ifdef __clang__
 #pragma GCC diagnostic ignored "-Wsign-conversion"
 #endif
 /* mbedTLS (as of v3.5.1) has a duplicate function declaration
diff --git a/src/openssl.c b/src/openssl.c
index 3032b94a..c3039ffe 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -160,7 +160,7 @@ int _libssh2_hmac_update(libssh2_hmac_ctx *ctx,
     return EVP_MAC_update(*ctx, data, datalen);
 #elif defined(HAVE_OPAQUE_STRUCTS)
 /* FIXME: upstream bug as of v5.7.0: datalen is int instead of size_t */
-#if defined(LIBSSH2_WOLFSSL)
+#ifdef LIBSSH2_WOLFSSL
     return HMAC_Update(*ctx, data, (int)datalen);
 #else /* !LIBSSH2_WOLFSSL */
     return HMAC_Update(*ctx, data, datalen);
@@ -452,7 +452,7 @@ _libssh2_rsa_sha2_verify(libssh2_rsa_ctx * rsactx,
     else {
 /* silence:
    warning C4701: potentially uninitialized local variable 'nid_type' used */
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
         nid_type = 0;
 #endif
         ret = -1; /* unsupported digest */
@@ -1293,7 +1293,7 @@ gen_publickey_from_rsa(LIBSSH2_SESSION *session, libssh2_rsa_ctx *rsa,
 #else
     const BIGNUM * e;
     const BIGNUM * n;
-#if defined(HAVE_OPAQUE_STRUCTS)
+#ifdef HAVE_OPAQUE_STRUCTS
     e = NULL;
     n = NULL;
 
diff --git a/src/scp.c b/src/scp.c
index c2ee194f..e39d7b5d 100644
--- a/src/scp.c
+++ b/src/scp.c
@@ -45,7 +45,7 @@
 
 #include <stdlib.h>  /* strtoll(), _strtoi64(), strtol() */
 
-#if defined(HAVE_STRTOLL)
+#ifdef HAVE_STRTOLL
 #define scpsize_strtol strtoll
 #elif defined(HAVE_STRTOI64)
 #define scpsize_strtol _strtoi64
diff --git a/src/session.c b/src/session.c
index baf4722b..12e9de51 100644
--- a/src/session.c
+++ b/src/session.c
@@ -60,7 +60,7 @@
 #include "channel.h"
 #include "mac.h"
 
-#if defined(_WIN32)
+#ifdef _WIN32
 #define libssh2_usec_t long
 #elif defined(__APPLE__)
 #define libssh2_usec_t suseconds_t
@@ -489,7 +489,7 @@ libssh2_session_init_ex(LIBSSH2_ALLOC_FUNC((*my_alloc)),
  * Set (or reset) a callback function
  * Returns the prior address
  */
-#if defined(__clang__)
+#ifdef __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wcast-function-type"
 #endif
@@ -557,7 +557,7 @@ libssh2_session_callback_set2(LIBSSH2_SESSION *session, int cbtype,
 
     return NULL;
 }
-#if defined(__clang__)
+#ifdef __clang__
 #pragma clang diagnostic pop
 #endif