diff --git a/lib11sht.c b/lib11sht.c
index 5d4f277..f38941e 100644
--- a/lib11sht.c
+++ b/lib11sht.c
@@ -203,7 +203,10 @@ static void asciify(const char *src, char *dest)
     if(!src || !dest)
         return;
     if(*src=='\0')
+    {
+        dest[0] = '\0';            /* maintain "dest is a valid C string" contract */
         return;
+    }
 
     j=i=0;
     while(src[i]!='\0' && i < LEVN_SBUFF)