diff --git a/src/if_mzsch.c b/src/if_mzsch.c
index 86e96bd..d6ee4b9 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -2649,7 +2649,8 @@
 	new_value = FALSE;
     else if (vim_value->v_type == VAR_STRING)
     {
-	result = scheme_make_string((char *)vim_value->vval.v_string);
+	result = scheme_make_string(vim_value->vval.v_string == NULL
+				    ? "" : (char *)vim_value->vval.v_string);
 	MZ_GC_CHECK();
     }
     else if (vim_value->v_type == VAR_NUMBER)