diff --git a/src/vm_x86.dasc b/src/vm_x86.dasc
index 5b3356dc..56712f90 100644
--- a/src/vm_x86.dasc
+++ b/src/vm_x86.dasc
@@ -1243,7 +1243,7 @@ static void build_subroutines(BuildCtx *ctx)
   |  mov LFUNC:RB, [RA-8]
   |  add NARGS:RD, 1
   |  // This is fragile. L->base must not move, KBASE must always be defined.
-  |.if x64
+  |.if X64
   |  cmp KBASEa, rdx			// Continue with CALLT if flag set.
   |.else
   |  cmp KBASE, BASE			// Continue with CALLT if flag set.