diff --git a/src/common/libscdl.c b/src/common/libscdl.c
index a78f9e2f..bc1d6b87 100644
--- a/src/common/libscdl.c
+++ b/src/common/libscdl.c
@@ -24,7 +24,7 @@
 
 #include "libscdl.h"
 
-#ifdef WIN32
+#ifdef _WIN32
 #include <windows.h>
 void *sc_dlopen(const char *filename)
 {
diff --git a/src/libopensc/internal-winscard.h b/src/libopensc/internal-winscard.h
index 2389d0c5..d2bb56e8 100644
--- a/src/libopensc/internal-winscard.h
+++ b/src/libopensc/internal-winscard.h
@@ -21,7 +21,7 @@ typedef unsigned __int8 uint8_t;
 #include <wintypes.h>
 #endif
 // allow unicode built where SCARD_READERSTATE is defined as SCARD_READERSTATEW and SCardGetStatusChange renamed to SCardGetStatusChangeW
-#ifdef WIN32
+#ifdef _WIN32
 #ifdef UNICODE
 #define SCARD_READERSTATE SCARD_READERSTATEA
 #undef SCardGetStatusChange