diff --git a/ntoskrnl/ex/zw.S b/ntoskrnl/ex/zw.S
index c619b9e1c43..2b1a77da057 100644
--- a/ntoskrnl/ex/zw.S
+++ b/ntoskrnl/ex/zw.S
@@ -2,6 +2,8 @@
 #include <asm.inc>
 #include <syscalls.inc>
 
+EXTERN _KiSystemService
+
 .code
 
 SyscallId = 0