diff --git a/lib/jsdoc/src/filter.js b/lib/jsdoc/src/filter.js
index f260a458..206206a3 100644
--- a/lib/jsdoc/src/filter.js
+++ b/lib/jsdoc/src/filter.js
@@ -11,6 +11,16 @@ var path = require('jsdoc/path');
 
 var pwd = env.pwd;
 
+function makeRegExp(config) {
+    var regExp = null;
+
+    if (config) {
+        regExp = (typeof config === 'string') ? new RegExp(config) : config;
+    }
+
+    return regExp;
+}
+
 /**
     @constructor
     @param {object} opts
@@ -24,12 +34,8 @@ exports.Filter = function(opts) {
             return path.resolve(pwd, $);
         }) :
         null;
-    this.includePattern = opts.includePattern?
-                            typeof opts.includePattern === 'string'? new RegExp(opts.includePattern) : opts.includePattern
-                            : null;
-    this.excludePattern = opts.excludePattern?
-                            typeof opts.excludePattern === 'string'? new RegExp(opts.excludePattern) : opts.excludePattern
-                            : null;
+    this.includePattern = makeRegExp(opts.includePattern);
+    this.excludePattern = makeRegExp(opts.excludePattern);
 };
 
 /**