diff --git a/spec/usageExamplesSpec.js b/spec/usageExamplesSpec.js
index 72ebcea..67f2d19 100755
--- a/spec/usageExamplesSpec.js
+++ b/spec/usageExamplesSpec.js
@@ -110,6 +110,20 @@ describe('Usage Examples', function () {
           someRandomThing: 'value B'
         });
       });
+      it('should also be available on instantiated config objects', function () {
+        process.env.SOME_PREFIX__MY_VAR = 'value A';
+        process.env.SOME_PREFIX__ANOTHER_VAR = 'value B';
+        var actual = new JsConfig({firstValue: 'set in constructor'});
+        actual.readFromObject(process.env, {
+          myVar: 'SOME_PREFIX__MY_VAR',
+          someRandomThing: 'SOME_PREFIX__ANOTHER_VAR'
+        });
+        expect(actual.getAll()).toEqual({
+          firstValue: 'set in constructor',
+          myVar: 'value A',
+          someRandomThing: 'value B'
+        });
+      });
       it('should remap string values into hierarchy', function () {
         process.env.SOME_PREFIX__MY_VAR = 'value A';
         process.env.SOME_PREFIX__ANOTHER_VAR = 'value B';
diff --git a/src/JsConfig.js b/src/JsConfig.js
index cc12cf9..dbc1b1f 100755
--- a/src/JsConfig.js
+++ b/src/JsConfig.js
@@ -115,29 +115,30 @@ var JsConfig = (function () {
         delete data[key];
       }
     };
-  }
 
-  JsConfig.readFromObject = function (obj, items) {
-    var missingKeys = [], output = new JsConfig();
-
-    function deepLoop(parent, combinedName) {
-      loop(parent, function (value, key) {
-        var name = combinedName ? combinedName + '.' : '';
-        name += key;
-        if (typeof value === 'object') {
-          deepLoop(value, name);
-        } else {
-          if (obj.hasOwnProperty(value)) {
-            output.set(name, obj[value]);
+    this.readFromObject = function (obj, items) {
+      var self = this;
+      function deepLoop(parent, combinedName) {
+        loop(parent, function (value, key) {
+          var name = combinedName ? combinedName + '.' : '';
+          name += key;
+          if (typeof value === 'object') {
+            deepLoop(value, name);
+          } else {
+            if (obj.hasOwnProperty(value)) {
+              self.set(name, obj[value]);
+            }
           }
-        }
-      });
-    }
+        });
+      }
 
-    deepLoop(items || {});
-    if (missingKeys.length > 0) {
-      throw new Error('Missing required configuration parameter [' + missingKeys.join(',') + '].');
-    }
+      deepLoop(items || {});
+    };
+  }
+
+  JsConfig.readFromObject = function () {
+    var output = new JsConfig();
+    output.readFromObject.apply(output, arguments);
     return output;
   };