diff --git a/AK/Platform.h b/AK/Platform.h
index 0e29cd09cf..4c93789d28 100644
--- a/AK/Platform.h
+++ b/AK/Platform.h
@@ -98,6 +98,10 @@
 #    define AK_OS_SOLARIS
 #endif
 
+#if defined(__HAIKU__)
+#    define AK_OS_HAIKU
+#endif
+
 #if defined(__gnu_hurd__)
 #    define AK_OS_GNU_HURD
 #endif