diff --git a/pomdog/audio/openal/prerequisites_openal.h b/pomdog/audio/openal/prerequisites_openal.h
index 2534701dd..154ed84dd 100644
--- a/pomdog/audio/openal/prerequisites_openal.h
+++ b/pomdog/audio/openal/prerequisites_openal.h
@@ -2,8 +2,17 @@
 
 #pragma once
 
+#include "pomdog/basic/conditional_compilation.h"
 #include "pomdog/basic/platform.h"
 
+#if defined(POMDOG_PLATFORM_MACOSX)
+// NOTE: For silencing OpenAL warnings on macOS >= 10.15.
+#ifndef OPENAL_DEPRECATED
+#define OPENAL_DEPRECATED
+#endif
+#endif
+
+POMDOG_SUPPRESS_WARNINGS_GENERATED_BY_STD_HEADERS_BEGIN
 #if defined(POMDOG_PLATFORM_MACOSX) || defined(POMDOG_PLATFORM_APPLE_IOS)
 #include <OpenAL/al.h>
 #include <OpenAL/alc.h>
@@ -11,3 +20,4 @@
 #include <AL/al.h>
 #include <AL/alc.h>
 #endif
+POMDOG_SUPPRESS_WARNINGS_GENERATED_BY_STD_HEADERS_END