diff --git a/CMakeLists.txt b/CMakeLists.txt
index a871f4c..f9f6b34 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -965,7 +965,8 @@ OPTION(ALSOFT_REQUIRE_DSOUND "Require DirectSound backend" OFF)
 OPTION(ALSOFT_REQUIRE_MMDEVAPI "Require MMDevApi backend" OFF)
 IF(HAVE_WINDOWS_H)
     # Check MMSystem backend
-    CHECK_INCLUDE_FILES("windows.h;mmsystem.h" HAVE_MMSYSTEM_H -D_WIN32_WINNT=0x0502)
+    set(CMAKE_REQUIRED_DEFINITIONS -D_WIN32_WINNT=0x0502)
+    CHECK_INCLUDE_FILES("windows.h;mmsystem.h" HAVE_MMSYSTEM_H)
     IF(HAVE_MMSYSTEM_H)
         CHECK_SHARED_FUNCTION_EXISTS(waveOutOpen "windows.h;mmsystem.h" winmm "" HAVE_LIBWINMM)
         IF(HAVE_LIBWINMM)
