diff --git a/lib/readline-sync.js b/lib/readline-sync.js
index 99bdb15..524308d 100644
--- a/lib/readline-sync.js
+++ b/lib/readline-sync.js
@@ -24,7 +24,7 @@ var
 function _readlineSync(display, options) {
   var input = '', rsize, err;
 
-  if (display !== '') {
+  if (display !== '') { // null and undefined were excluded.
     if (typeof print === 'function') { print(display, encoding); }
     stdout.write(display + '', encoding);
   }
@@ -154,8 +154,10 @@ exports.setPrint = function(fnc) { print = fnc; };
 
 exports.setPrompt = function(newPrompt) {
 /* jshint eqnull:true */
-  promptText = newPrompt != null ? newPrompt : '';
+  if (newPrompt != null) {
 /* jshint eqnull:false */
+    promptText = newPrompt;
+  }
   return promptText;
 };
 
diff --git a/package.json b/package.json
index 2f0d7e7..356ccde 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "readline-sync",
   "description": "Synchronous Readline",
-  "version": "0.4.4",
+  "version": "0.4.5",
   "homepage": "https://github.com/anseki/readline-sync",
   "author": {
     "name": "anseki"