diff --git a/examples/iscsiclient.c b/examples/iscsiclient.c
index 95dbe87..476a925 100644
--- a/examples/iscsiclient.c
+++ b/examples/iscsiclient.c
@@ -34,7 +34,7 @@
 /* This is the host/port we connect to.*/
 #define TARGET "127.0.0.1:3260"
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include "win32/win32_compat.h"
 #pragma comment(lib, "ws2_32.lib")
@@ -625,7 +625,7 @@ int main(int argc _U_, char *argv[] _U_)
 	struct client_state clnt;
 
 	printf("iscsi client\n");
-#if defined(WIN32)
+#if defined(_WIN32)
 	if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {
 		printf("Failed to start Winsock2\n");
 		exit(10);
diff --git a/include/iscsi-private.h b/include/iscsi-private.h
index a85b4bd..aedbbe0 100644
--- a/include/iscsi-private.h
+++ b/include/iscsi-private.h
@@ -20,7 +20,7 @@
 #include <stdint.h>
 #include <time.h>
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <basetsd.h>
 #define ssize_t SSIZE_T
 #endif
@@ -324,7 +324,7 @@ int iscsi_process_reject(struct iscsi_context *iscsi,
 				struct iscsi_in_pdu *in);
 int iscsi_send_target_nop_out(struct iscsi_context *iscsi, uint32_t ttt, uint32_t lun);
 
-#if defined(WIN32)
+#if defined(_WIN32)
 void iscsi_set_error(struct iscsi_context *iscsi, const char *error_string,
 		     ...);
 #else
diff --git a/include/iscsi.h b/include/iscsi.h
index 798703c..63fa94b 100644
--- a/include/iscsi.h
+++ b/include/iscsi.h
@@ -20,7 +20,7 @@
 #include <stdint.h>
 #include <sys/types.h>
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #define EXTERN __declspec( dllexport )
 #else
 #define EXTERN
diff --git a/include/md5.h b/include/md5.h
index 52ba252..c5cdd0e 100644
--- a/include/md5.h
+++ b/include/md5.h
@@ -23,7 +23,7 @@
 #ifndef MD5_H
 #define MD5_H
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #else
 #include <netinet/in.h>
 #endif
diff --git a/include/scsi-lowlevel.h b/include/scsi-lowlevel.h
index 2b1e407..f2a8908 100644
--- a/include/scsi-lowlevel.h
+++ b/include/scsi-lowlevel.h
@@ -17,7 +17,7 @@
 #ifndef __scsi_lowlevel_h__
 #define __scsi_lowlevel_h__
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #define EXTERN __declspec( dllexport )
 #else
 #define EXTERN
diff --git a/lib/connect.c b/lib/connect.c
index 989b924..4043f7c 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -15,7 +15,7 @@
    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
-#if defined(WIN32)
+#if defined(_WIN32)
 #include "win32/win32_compat.h"
 #else
 #include <unistd.h>
diff --git a/lib/crc32c.c b/lib/crc32c.c
index 4455171..3c9d6a5 100644
--- a/lib/crc32c.c
+++ b/lib/crc32c.c
@@ -15,7 +15,7 @@
    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
-#if defined(WIN32)
+#if defined(_WIN32)
 #else
 #include <unistd.h>
 #endif
diff --git a/lib/init.c b/lib/init.c
index 88bc7eb..34a95a5 100644
--- a/lib/init.c
+++ b/lib/init.c
@@ -21,7 +21,7 @@
 
 #define _GNU_SOURCE
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include "win32/win32_compat.h"
 #else
 #include <strings.h>
diff --git a/lib/iscsi-command.c b/lib/iscsi-command.c
index f9ca8e0..5be7ee2 100644
--- a/lib/iscsi-command.c
+++ b/lib/iscsi-command.c
@@ -27,7 +27,7 @@
 #include <arpa/inet.h>
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #endif
 
diff --git a/lib/logging.c b/lib/logging.c
index bc31f24..be518fc 100644
--- a/lib/logging.c
+++ b/lib/logging.c
@@ -31,7 +31,7 @@
 #include <unistd.h>
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include "win32/win32_compat.h"
 #endif
 
diff --git a/lib/login.c b/lib/login.c
index 36de085..e2bb112 100644
--- a/lib/login.c
+++ b/lib/login.c
@@ -32,7 +32,7 @@
 #include <arpa/inet.h>
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include "win32/win32_compat.h"
 #endif
diff --git a/lib/nop.c b/lib/nop.c
index 6d9f450..b2104cd 100644
--- a/lib/nop.c
+++ b/lib/nop.c
@@ -16,7 +16,7 @@
    along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #else
 #include <unistd.h>
 #endif
diff --git a/lib/pdu.c b/lib/pdu.c
index 6fd4b45..0bcbe11 100644
--- a/lib/pdu.c
+++ b/lib/pdu.c
@@ -34,7 +34,7 @@
 #define PRIx32 "x"
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include "win32/win32_compat.h"
diff --git a/lib/scsi-lowlevel.c b/lib/scsi-lowlevel.c
index 0558e5b..d68d990 100644
--- a/lib/scsi-lowlevel.c
+++ b/lib/scsi-lowlevel.c
@@ -38,7 +38,7 @@
 #include "aros/aros_compat.h"
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include "win32/win32_compat.h"
 #else
diff --git a/lib/socket.c b/lib/socket.c
index 22e6e57..4aa0d9a 100644
--- a/lib/socket.c
+++ b/lib/socket.c
@@ -43,7 +43,7 @@
 #include <sys/socket.h>
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include "win32/win32_compat.h"
@@ -139,7 +139,7 @@ void iscsi_decrement_iface_rr() {
 
 static int set_nonblocking(int fd)
 {
-#if defined(WIN32)
+#if defined(_WIN32)
 	unsigned long opt = 1;
 	return ioctlsocket(fd, FIONBIO, &opt);
 #else
@@ -272,7 +272,7 @@ static int iscsi_tcp_connect(struct iscsi_context *iscsi, union socket_address *
 	}
 
 	if (connect(iscsi->fd, &sa->sa, socksize) != 0
-#if defined(WIN32)
+#if defined(_WIN32)
             && WSAGetLastError() != WSAEWOULDBLOCK
 #endif
             && errno != EINPROGRESS) {
diff --git a/lib/sync.c b/lib/sync.c
index 1c2084e..ce59c29 100644
--- a/lib/sync.c
+++ b/lib/sync.c
@@ -27,7 +27,7 @@
 #include "aros/aros_compat.h"
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include "win32/win32_compat.h"
 #endif
diff --git a/utils/iscsi-ls.c b/utils/iscsi-ls.c
index 2c4dbc6..95ab1a6 100644
--- a/utils/iscsi-ls.c
+++ b/utils/iscsi-ls.c
@@ -19,7 +19,7 @@
 #include "config.h"
 #endif
 
-#if defined(WIN32)
+#if defined(_WIN32)
 #include <winsock2.h>
 #include "win32_compat.h"
 #pragma comment(lib, "ws2_32.lib")
@@ -354,7 +354,7 @@ int main(int argc, char *argv[])
 	int i;
 	static int show_help = 0, show_usage = 0, debug = 0;
 
-#ifdef WIN32
+#ifdef _WIN32
 	if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {
 		printf("Failed to start Winsock2\n");
 		exit(10);
diff --git a/win32/win32_compat.c b/win32/win32_compat.c
index 8c797be..d6bece5 100644
--- a/win32/win32_compat.c
+++ b/win32/win32_compat.c
@@ -21,7 +21,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
-#ifndef WIN32
+#ifndef _WIN32
 
 static int dummy ATTRIBUTE((unused));
 
diff --git a/win32/win32_compat.h b/win32/win32_compat.h
index 8ec388a..f30269a 100644
--- a/win32/win32_compat.h
+++ b/win32/win32_compat.h
@@ -25,7 +25,7 @@ THE SOFTWARE.
 #ifndef win32_COMPAT_H_
 #define win32_COMPAT_H_
 
-#ifdef WIN32
+#ifdef _WIN32
 #define NO_IPv6 1
 
 #include <winsock2.h>
@@ -90,5 +90,5 @@ struct iovec {
 
 #define inline
 
-#endif // WIN32
+#endif // _WIN32
 #endif // win32_COMPAT_H_