diff --git a/subsystems/win32/csrss/csrss.c b/subsystems/win32/csrss/csrss.c
index 7dd97df16c7..a4205d5f3b0 100644
--- a/subsystems/win32/csrss/csrss.c
+++ b/subsystems/win32/csrss/csrss.c
@@ -43,7 +43,9 @@ _main(int argc,
 {
     KPRIORITY BasePriority = (8 + 1) + 4;
     NTSTATUS Status;
+#if defined (_X86_)
     ULONG Response;
+#endif
     UNREFERENCED_PARAMETER(envp);
     UNREFERENCED_PARAMETER(DebugFlag);