diff --git a/index.js b/index.js
index 9f668d42..35957f25 100644
--- a/index.js
+++ b/index.js
@@ -37,26 +37,28 @@ queryResult = {
 //      - within 'pg-promise'.
 //
 //    promiseLib: null
-//      - Overrides the promise library instance to be used
-//        by the library.
+//      - Overrides the promise library instance used by
+//        the library.
 // }
 module.exports = function (options) {
 
     if (npm) {
         throw new Error('Cannot initialize the library more than once.');
     } else {
-        npm = {
-            pg: require('pg')
-        };
+        var promiseLib;
         if (options && options.promiseLib) {
             if (typeof(options.promiseLib) === 'function') {
-                npm.promise = options.promiseLib;
+                promiseLib = options.promiseLib;
             } else {
                 throw new Error('Invalid or unsupported promise library override.');
             }
         } else {
-            npm.promise = require('promise');
+            promiseLib = require('promise');
         }
+        npm = {
+            pg: require('pg'),
+            promise: promiseLib
+        };
     }
 
     var lib = function (cn) {
diff --git a/test/indexSpec.js b/test/indexSpec.js
index bbf19968..5f010c37 100644
--- a/test/indexSpec.js
+++ b/test/indexSpec.js
@@ -1,23 +1,34 @@
-var pgpLib = require('../index')
+var pgpLib = require('../index');
+var pgp = pgpLib(); // initializing the library;
 
 describe("Library entry object", function () {
+
     it("must be a function", function () {
         expect(typeof(pgpLib)).toBe('function');
     });
-});
 
-var pgp = pgpLib(); // initializing the library;
+});
 
 describe("Library initialization object", function () {
+
+    it("can be created only once", function () {
+        expect(function(){
+            pgpLib();
+        }).toThrow('Cannot initialize the library more than once.');
+    });
+
     it("must be a function", function () {
         expect(typeof(pgp)).toBe('function');
     });
+
     it("must have property 'pg'", function () {
         expect(typeof(pgp.pg)).toBe('object');
     });
+
     it("must have function 'end'", function () {
         expect(typeof(pgp.end)).toBe('function');
     });
+
     it("must have valid property 'as'", function () {
         expect(typeof(pgp.as)).toBe('object');
         expect(typeof(pgp.as.text)).toBe('function');