diff --git a/src/lisp/x86-validate-linux.h b/src/lisp/x86-validate-linux.h
index 3d9f3cd22f932187c70935d1260bb9ae43efa6ec..7b22a1aaaa7cd2743f694a78bcdea3ed1ba3b9ec 100644
--- a/src/lisp/x86-validate-linux.h
+++ b/src/lisp/x86-validate-linux.h
@@ -45,17 +45,17 @@
 #define STATIC_SPACE_START	(SpaceStart_TargetStatic)
 #define STATIC_SPACE_SIZE	(0x0ffff000)	/* 256MB - 1 page */
 
-#ifdef RELOCATABLE_STACK_START
+#ifndef RELOCATABLE_STACK_START
 #define BINDING_STACK_START	(0x20000000)
 #endif
 #define BINDING_STACK_SIZE	(0x07fff000)	/* 128MB - 1 page */
 
-#ifdef RELOCATABLE_STACK_START
+#ifndef RELOCATABLE_STACK_START
 #define CONTROL_STACK_START	0x38000000
 #endif
 #define CONTROL_STACK_SIZE	(0x07fff000 - 8192)
 
-#ifdef RELOCATABLE_STACK_START
+#ifndef RELOCATABLE_STACK_START
 #define SIGNAL_STACK_START	CONTROL_STACK_END
 #endif
 #define SIGNAL_STACK_SIZE	SIGSTKSZ