diff --git a/balloc.c b/balloc.c
index 63967f60ce84..5aa9b4ab80de 100644
--- a/balloc.c
+++ b/balloc.c
@@ -30,6 +30,10 @@
 #error "BITS_PER_LONG not 32 or 64"
 #endif
 
+#ifndef ALIGN_DOWN
+#define ALIGN_DOWN(x, a) __ALIGN_KERNEL((x) - ((a) - 1), (a))
+#endif 
+
 /*
  *  Allocation Bitmap Management Functions
  */