diff --git a/src/lisp/x86-validate-darwin.h b/src/lisp/x86-validate-darwin.h
index 1ac37f3d0b1a16dd4a4c699352485e3e1e47bda4..d6b956d21c6bc52192fa687e62cabd7125fb2290 100644
--- a/src/lisp/x86-validate-darwin.h
+++ b/src/lisp/x86-validate-darwin.h
@@ -23,7 +23,7 @@
 #endif
 #define BINDING_STACK_SIZE	(0x07fff000)	/* 128MB - 1 page */
 
-#ifdef RELOCATABLE_STACK_START
+#ifndef RELOCATABLE_STACK_START
 #define CONTROL_STACK_START	(0x40000000)
 #endif