diff --git a/README.md b/README.md
index c6fb8ae..b2b8c9d 100644
--- a/README.md
+++ b/README.md
@@ -147,10 +147,10 @@ _The ui-ace directive stores and expects the model value to be a standard javasc
 
 Simple demo
 ```html
-<div ui-ace readonly="true"></div>
+<div ui-ace readonly></div>
 or
 Check me to make Ace readonly: <input type="checkbox" ng-model="checked" ><br/>
-<div ui-ace readonly="{{checked}}"></div>
+<div ui-ace ng-readonly="checked"></div>
 ```
 
 ### Ace instance direct access
diff --git a/src/ui-ace.js b/src/ui-ace.js
index 169145a..43ae7f7 100644
--- a/src/ui-ace.js
+++ b/src/ui-ace.js
@@ -248,7 +248,7 @@ angular.module('ui.ace', [])
         };
 
         attrs.$observe('readonly', function (value) {
-          acee.setReadOnly(value === 'true');
+          acee.setReadOnly(!!value || value === '');
         });
 
         // Value Blind
diff --git a/test/ace.spec.js b/test/ace.spec.js
index 405bb9a..af7cdc4 100644
--- a/test/ace.spec.js
+++ b/test/ace.spec.js
@@ -136,6 +136,8 @@ describe('uiAce', function () {
         .createSpy('window.ace.edit')
         .and.callFake(function () {
           _ace = aceEditFunction.apply(this, arguments);
+          _ace.setReadOnly = jasmine.createSpy('ace.setReadOnly')
+            .and.callThrough();
           return _ace;
         });
     });
@@ -177,27 +179,40 @@ describe('uiAce', function () {
     });
 
     describe('readOnly', function () {
+
       it('should read only option true', function () {
-        $compile('<div ui-ace readonly="true">')(scope);
+        $compile('<div ui-ace readonly>')(scope);
+        scope.$apply();
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(true);
+
+        $compile('<div ui-ace ng-readonly="true">')(scope);
         scope.$apply();
-        expect(_ace.getReadOnly()).toBeTruthy();
-        $compile('<div ui-ace readonly="{{foo}}">')(scope);
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(true);
+
+        $compile('<div ui-ace ng-readonly="foo">')(scope);
         scope.$apply('foo = true');
-        expect(_ace.getReadOnly()).toBeTruthy();
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(true);
+
       });
+
       it('should read only option false', function () {
         $compile('<div ui-ace>')(scope);
         scope.$apply();
-        expect(_ace.getReadOnly()).toBeFalsy();
-        $compile('<div ui-ace readonly="false">')(scope);
+        expect(_ace.setReadOnly).not.toHaveBeenCalled();
+
+        $compile('<div ui-ace ng-readonly="false">')(scope);
         scope.$apply();
-        expect(_ace.getReadOnly()).toBeFalsy();
-        $compile('<div ui-ace readonly="{{foo}}">')(scope);
-        expect(_ace.getReadOnly()).toBeFalsy();
-        scope.$apply('foo = true');
-        expect(_ace.getReadOnly()).toBeTruthy();
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(false);
+
+        $compile('<div ui-ace ng-readonly="foo">')(scope);
+        scope.$apply();
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(false);
+
+        scope.$apply('foo = null');
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(false);
+
         scope.$apply('foo = false');
-        expect(_ace.getReadOnly()).toBeFalsy();
+        expect(_ace.setReadOnly).toHaveBeenCalledWith(false);
       });
     });