diff --git a/include/internal/catch_session.cpp b/include/internal/catch_session.cpp
index 5aee5d99..f9818f74 100644
--- a/include/internal/catch_session.cpp
+++ b/include/internal/catch_session.cpp
@@ -197,7 +197,7 @@ namespace Catch {
         return 0;
     }
 
-#if defined(CATCH_CONFIG_WCHAR) && defined(WIN32) && defined(UNICODE)
+#if defined(CATCH_CONFIG_WCHAR) && defined(_WIN32) && defined(UNICODE)
     int Session::applyCommandLine( int argc, wchar_t const * const * argv ) {
 
         char **utf8Argv = new char *[ argc ];
diff --git a/include/internal/catch_session.h b/include/internal/catch_session.h
index af820da4..4e83d520 100644
--- a/include/internal/catch_session.h
+++ b/include/internal/catch_session.h
@@ -26,7 +26,7 @@ namespace Catch {
         void libIdentify();
 
         int applyCommandLine( int argc, char const * const * argv );
-    #if defined(CATCH_CONFIG_WCHAR) && defined(WIN32) && defined(UNICODE)
+    #if defined(CATCH_CONFIG_WCHAR) && defined(_WIN32) && defined(UNICODE)
         int applyCommandLine( int argc, wchar_t const * const * argv );
     #endif