diff --git a/sh.h b/sh.h
index 4c95582..daceb90 100644
--- a/sh.h
+++ b/sh.h
@@ -150,7 +150,7 @@
 #endif
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.377 2010/01/28 15:13:25 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.378 2010/01/28 20:26:51 tg Exp $");
 #endif
 #define MKSH_VERSION "R39 2010/01/08"
 
@@ -1624,7 +1624,8 @@ char *str_val(struct tbl *);
 int setstr(struct tbl *, const char *, int);
 struct tbl *setint_v(struct tbl *, struct tbl *, bool);
 void setint(struct tbl *, mksh_ari_t);
-struct tbl *typeset(const char *, Tflag, Tflag, int, int);
+struct tbl *typeset(const char *, Tflag, Tflag, int, int)
+    MKSH_A_NONNULL((nonnull (1)));
 void unset(struct tbl *, int);
 const char *skip_varname(const char *, int);
 const char *skip_wdvarname(const char *, int);
diff --git a/var.c b/var.c
index 1724e18..3a8052a 100644
--- a/var.c
+++ b/var.c
@@ -22,7 +22,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/var.c,v 1.103 2010/01/25 14:38:04 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/var.c,v 1.104 2010/01/28 20:26:52 tg Exp $");
 
 /*
  * Variables
@@ -680,6 +680,8 @@ typeset(const char *var, Tflag set, Tflag clr, int field, int base)
 	val = skip_varname(var, false);
 	if (val == var)
 		return (NULL);
+	mkssert(var != NULL);
+	mkssert(*var != 0);
 	if (*val == '[') {
 		if (set_refflag)
 			errorf("%s: reference variable cannot be an array",