diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
index eba2e3d..8d0b1cd 100644
--- a/include/asm-mips/system.h
+++ b/include/asm-mips/system.h
@@ -470,6 +470,6 @@
  */
 #define __ARCH_WANT_UNLOCKED_CTXSW
 
-#define arch_align_stack(x) (x)
+extern unsigned long arch_align_stack(unsigned long sp);
 
 #endif /* _ASM_SYSTEM_H */