diff --git a/AK/Platform.h b/AK/Platform.h
index 0d6801cab7..8842a201cd 100644
--- a/AK/Platform.h
+++ b/AK/Platform.h
@@ -47,6 +47,7 @@
 
 #ifndef __serenity__
 #    include <unistd.h>
+#    undef PAGE_SIZE
 #    define PAGE_SIZE sysconf(_SC_PAGESIZE)
 #endif