diff --git a/mach/i386/ncg/mach.c b/mach/i386/ncg/mach.c
index 1497974be..34a4b6f16 100644
--- a/mach/i386/ncg/mach.c
+++ b/mach/i386/ncg/mach.c
@@ -140,7 +140,7 @@ f_regsave()
 
 void
 regsave(regstr, off, size)
-	char *regstr;
+	const char *regstr;
 	long off;
 {
 	if (strcmp(regstr, "esi") == 0) {
diff --git a/mach/i86/ncg/mach.c b/mach/i86/ncg/mach.c
index 817599147..d93eaba3d 100644
--- a/mach/i86/ncg/mach.c
+++ b/mach/i86/ncg/mach.c
@@ -137,7 +137,7 @@ f_regsave()
 
 void
 regsave(regstr, off, size)
-	char *regstr;
+	const char *regstr;
 	long off;
 {
 	if (strcmp(regstr, "si") == 0) {
diff --git a/mach/m68020/ncg/mach.c b/mach/m68020/ncg/mach.c
index 4f710348d..f230761c4 100644
--- a/mach/m68020/ncg/mach.c
+++ b/mach/m68020/ncg/mach.c
@@ -184,7 +184,7 @@ f_regsave()
 
 void
 regsave(s,off,size)
-	char *s;
+	const char *s;
 	long off;
 {
 	assert (regnr < 9);