diff --git a/src/lisp/ppc-validate.h b/src/lisp/ppc-validate.h
index 1959dc8d52ce2479f0c0923f66b41e56bbd76968..e4c215f96a06832a132a3e05736fc616c392ab8e 100644
--- a/src/lisp/ppc-validate.h
+++ b/src/lisp/ppc-validate.h
@@ -49,6 +49,8 @@
 #define CONTROL_STACK_END       (CONTROL_STACK_START + control_stack_size)
 #endif
 
+#define SIGNAL_STACK_SIZE	SIGSTKSZ
+
 #if 0
 #define BINDING_STACK_START 	(0x38000000)
 #endif
diff --git a/src/lisp/sparc-validate.h b/src/lisp/sparc-validate.h
index e3a88d74453c9acaa62bc45fe5b7c3e40a746f31..b8fad15c6b6df508d5b8a0d0f98d3387e445978a 100644
--- a/src/lisp/sparc-validate.h
+++ b/src/lisp/sparc-validate.h
@@ -109,6 +109,8 @@
 #define CONTROL_STACK_END       (CONTROL_STACK_START + control_stack_size)
 #endif
 
+#define SIGNAL_STACK_SIZE	SIGSTKSZ
+
 #define DYNAMIC_0_SPACE_START	(SpaceStart_TargetDynamic)
 
 /* This isn't used with GENCGC */