diff --git a/release/angular-recaptcha.js b/release/angular-recaptcha.js
index 907dab5..38f6163 100644
--- a/release/angular-recaptcha.js
+++ b/release/angular-recaptcha.js
@@ -1,7 +1,7 @@
 /**
- * @license angular-recaptcha build:2017-11-22
+ * @license angular-recaptcha build:2018-01-03
  * https://github.com/vividcortex/angular-recaptcha
- * Copyright (c) 2017 VividCortex
+ * Copyright (c) 2018 VividCortex
 **/
 
 /*global angular, Recaptcha */
@@ -295,11 +295,11 @@
 
     var app = ng.module('vcRecaptcha');
 
-    app.directive('vcRecaptcha', ['$document', '$timeout', 'vcRecaptchaService', function ($document, $timeout, vcRecaptcha) {
+    app.directive('vcRecaptcha', ['$document', '$timeout', 'vcRecaptchaService', '$q', function ($document, $timeout, vcRecaptcha, $q) {
 
         return {
             restrict: 'A',
-            require: "?^^form",
+            require: '?^^form',
             scope: {
                 response: '=?ngModel',
                 key: '=?',
@@ -318,11 +318,16 @@
             link: function (scope, elm, attrs, ctrl) {
                 scope.widgetId = null;
 
-                if(ctrl && ng.isDefined(attrs.required)){
+                if (ctrl && ng.isDefined(attrs.required)) {
                     scope.$watch('required', validate);
                 }
 
                 var removeCreationListener = scope.$watch('key', function (key) {
+                    // Abort if undefined or null
+                    if (ng.isUndefined(key) || key === null) {
+                        return;
+                    }
+
                     var callback = function (gRecaptchaResponse) {
                         // Safe $apply
                         $timeout(function () {
@@ -334,19 +339,20 @@
                         });
                     };
 
-                    vcRecaptcha.create(elm[0], {
-
-                        callback: callback,
-                        key: key,
-                        stoken: scope.stoken || attrs.stoken || null,
-                        theme: scope.theme || attrs.theme || null,
-                        type: scope.type || attrs.type || null,
-                        lang: scope.lang || attrs.lang || null,
-                        tabindex: scope.tabindex || attrs.tabindex || null,
-                        size: scope.size || attrs.size || null,
-                        badge: scope.badge || attrs.badge || null,
-                        'expired-callback': expired
-
+                    // Accept a promise, or resolve immediately if the value is a bare string
+                    $q.resolve(key).then(function (resolved) {
+                        return vcRecaptcha.create(elm[0], {
+                            callback: callback,
+                            key: resolved,
+                            stoken: scope.stoken || attrs.stoken || null,
+                            theme: scope.theme || attrs.theme || null,
+                            type: scope.type || attrs.type || null,
+                            lang: scope.lang || attrs.lang || null,
+                            tabindex: scope.tabindex || attrs.tabindex || null,
+                            size: scope.size || attrs.size || null,
+                            badge: scope.badge || attrs.badge || null,
+                            'expired-callback': expired
+                        });
                     }).then(function (widgetId) {
                         // The widget has been created
                         validate();
@@ -355,13 +361,12 @@
 
                         scope.$on('$destroy', destroy);
 
-                        scope.$on('reCaptchaReset', function(event, resetWidgetId){
-                          if(ng.isUndefined(resetWidgetId) || widgetId === resetWidgetId){
-                            scope.response = "";
-                            validate();
-                          }
-                        })
-
+                        scope.$on('reCaptchaReset', function (event, resetWidgetId) {
+                            if (ng.isUndefined(resetWidgetId) || widgetId === resetWidgetId) {
+                                scope.response = '';
+                                validate();
+                            }
+                        });
                     });
 
                     // Remove this listener to avoid creating the widget more than once.
@@ -369,36 +374,36 @@
                 });
 
                 function destroy() {
-                  if (ctrl) {
-                    // reset the validity of the form if we were removed
-                    ctrl.$setValidity('recaptcha', null);
-                  }
+                    if (ctrl) {
+                        // reset the validity of the form if we were removed
+                        ctrl.$setValidity('recaptcha', null);
+                    }
 
-                  cleanup();
+                    cleanup();
                 }
 
-                function expired(){
+                function expired() {
                     // Safe $apply
                     $timeout(function () {
-                        scope.response = "";
+                        scope.response = '';
                         validate();
 
                         // Notify about the response availability
-                        scope.onExpire({ widgetId: scope.widgetId });
+                        scope.onExpire({widgetId: scope.widgetId});
                     });
                 }
 
-                function validate(){
-                    if(ctrl){
+                function validate() {
+                    if (ctrl) {
                         ctrl.$setValidity('recaptcha', scope.required === false ? null : Boolean(scope.response));
                     }
                 }
 
-                function cleanup(){
-                  vcRecaptcha.destroy(scope.widgetId);
+                function cleanup() {
+                    vcRecaptcha.destroy(scope.widgetId);
 
-                  // removes elements reCaptcha added.
-                  ng.element($document[0].querySelectorAll('.pls-container')).parent().remove();
+                    // removes elements reCaptcha added.
+                    ng.element($document[0].querySelectorAll('.pls-container')).parent().remove();
                 }
             }
         };
diff --git a/release/angular-recaptcha.min.js b/release/angular-recaptcha.min.js
index 759666c..d0450fd 100644
--- a/release/angular-recaptcha.min.js
+++ b/release/angular-recaptcha.min.js
@@ -1,8 +1,8 @@
 /**
- * @license angular-recaptcha build:2017-11-22
+ * @license angular-recaptcha build:2018-01-03
  * https://github.com/vividcortex/angular-recaptcha
- * Copyright (c) 2017 VividCortex
+ * Copyright (c) 2018 VividCortex
 **/
 
 
-!function(a){"use strict";a.module("vcRecaptcha",[])}(angular),function(a){"use strict";function b(){throw new Error('You need to set the "key" attribute to your public reCaptcha key. If you don\'t have a key, please get one from https://www.google.com/recaptcha/admin/create')}a.module("vcRecaptcha").provider("vcRecaptchaService",function(){var c=this,d={};c.onLoadFunctionName="vcRecaptchaApiLoaded",c.setDefaults=function(b){a.copy(b,d)},c.setSiteKey=function(a){d.key=a},c.setTheme=function(a){d.theme=a},c.setStoken=function(a){d.stoken=a},c.setSize=function(a){d.size=a},c.setType=function(a){d.type=a},c.setLang=function(a){d.lang=a},c.setBadge=function(a){d.badge=a},c.setOnLoadFunctionName=function(a){c.onLoadFunctionName=a},c.$get=["$rootScope","$window","$q","$document","$interval",function(e,f,g,h,i){function j(){return l?g.when(l):n}function k(){if(!l)throw new Error("reCaptcha has not been loaded yet.")}var l,m=g.defer(),n=m.promise,o={};f.vcRecaptchaApiLoadedCallback=f.vcRecaptchaApiLoadedCallback||[];var p=function(){l=f.grecaptcha,m.resolve(l)};if(f.vcRecaptchaApiLoadedCallback.push(p),f[c.onLoadFunctionName]=function(){f.vcRecaptchaApiLoadedCallback.forEach(function(a){a()})},a.isDefined(f.grecaptcha))p();else if(f.document.querySelector('script[src^="https://www.google.com/recaptcha/api.js"]'))var q=i(function(){a.isDefined(f.grecaptcha)&&(i.cancel(q),p())},25);else{var r=f.document.createElement("script");r.async=!0,r.defer=!0,r.src="https://www.google.com/recaptcha/api.js?onload="+c.onLoadFunctionName+"&render=explicit",h.find("body")[0].appendChild(r)}return{create:function(a,c){return c.sitekey=c.key||d.key,c.theme=c.theme||d.theme,c.stoken=c.stoken||d.stoken,c.size=c.size||d.size,c.type=c.type||d.type,c.hl=c.lang||d.lang,c.badge=c.badge||d.badge,c.sitekey&&40===c.sitekey.length||b(),j().then(function(b){var d=b.render(a,c);return o[d]=a,d})},reload:function(a){k(),l.reset(a),e.$broadcast("reCaptchaReset",a)},execute:function(a){k(),l.execute(a)},useLang:function(a,b){var c=o[a];if(!c)throw new Error("reCaptcha Widget ID not exists",a);var d=c.querySelector("iframe");if(!b)return d&&d.src&&/[?&]hl=\w+/.test(d.src)?d.src.replace(/.+[?&]hl=(\w+)([^\w].+)?/,"$1"):null;if(d&&d.src){var e=d.src;/[?&]hl=/.test(e)?e=e.replace(/([?&]hl=)\w+/,"$1"+b):e+=(-1===e.indexOf("?")?"?":"&")+"hl="+b,d.src=e}},getResponse:function(a){return k(),l.getResponse(a)},getInstance:function(a){return o[a]},destroy:function(a){delete o[a]}}}]})}(angular),function(a){"use strict";a.module("vcRecaptcha").directive("vcRecaptcha",["$document","$timeout","vcRecaptchaService",function(b,c,d){return{restrict:"A",require:"?^^form",scope:{response:"=?ngModel",key:"=?",stoken:"=?",theme:"=?",size:"=?",type:"=?",lang:"=?",badge:"=?",tabindex:"=?",required:"=?",onCreate:"&",onSuccess:"&",onExpire:"&"},link:function(e,f,g,h){function i(){h&&h.$setValidity("recaptcha",null),l()}function j(){c(function(){e.response="",k(),e.onExpire({widgetId:e.widgetId})})}function k(){h&&h.$setValidity("recaptcha",!1===e.required?null:Boolean(e.response))}function l(){d.destroy(e.widgetId),a.element(b[0].querySelectorAll(".pls-container")).parent().remove()}e.widgetId=null,h&&a.isDefined(g.required)&&e.$watch("required",k);var m=e.$watch("key",function(b){var h=function(a){c(function(){e.response=a,k(),e.onSuccess({response:a,widgetId:e.widgetId})})};d.create(f[0],{callback:h,key:b,stoken:e.stoken||g.stoken||null,theme:e.theme||g.theme||null,type:e.type||g.type||null,lang:e.lang||g.lang||null,tabindex:e.tabindex||g.tabindex||null,size:e.size||g.size||null,badge:e.badge||g.badge||null,"expired-callback":j}).then(function(b){k(),e.widgetId=b,e.onCreate({widgetId:b}),e.$on("$destroy",i),e.$on("reCaptchaReset",function(c,d){(a.isUndefined(d)||b===d)&&(e.response="",k())})}),m()})}}}])}(angular);
\ No newline at end of file
+!function(a){"use strict";a.module("vcRecaptcha",[])}(angular),function(a){"use strict";function b(){throw new Error('You need to set the "key" attribute to your public reCaptcha key. If you don\'t have a key, please get one from https://www.google.com/recaptcha/admin/create')}a.module("vcRecaptcha").provider("vcRecaptchaService",function(){var c=this,d={};c.onLoadFunctionName="vcRecaptchaApiLoaded",c.setDefaults=function(b){a.copy(b,d)},c.setSiteKey=function(a){d.key=a},c.setTheme=function(a){d.theme=a},c.setStoken=function(a){d.stoken=a},c.setSize=function(a){d.size=a},c.setType=function(a){d.type=a},c.setLang=function(a){d.lang=a},c.setBadge=function(a){d.badge=a},c.setOnLoadFunctionName=function(a){c.onLoadFunctionName=a},c.$get=["$rootScope","$window","$q","$document","$interval",function(e,f,g,h,i){function j(){return l?g.when(l):n}function k(){if(!l)throw new Error("reCaptcha has not been loaded yet.")}var l,m=g.defer(),n=m.promise,o={};f.vcRecaptchaApiLoadedCallback=f.vcRecaptchaApiLoadedCallback||[];var p=function(){l=f.grecaptcha,m.resolve(l)};if(f.vcRecaptchaApiLoadedCallback.push(p),f[c.onLoadFunctionName]=function(){f.vcRecaptchaApiLoadedCallback.forEach(function(a){a()})},a.isDefined(f.grecaptcha))p();else if(f.document.querySelector('script[src^="https://www.google.com/recaptcha/api.js"]'))var q=i(function(){a.isDefined(f.grecaptcha)&&(i.cancel(q),p())},25);else{var r=f.document.createElement("script");r.async=!0,r.defer=!0,r.src="https://www.google.com/recaptcha/api.js?onload="+c.onLoadFunctionName+"&render=explicit",h.find("body")[0].appendChild(r)}return{create:function(a,c){return c.sitekey=c.key||d.key,c.theme=c.theme||d.theme,c.stoken=c.stoken||d.stoken,c.size=c.size||d.size,c.type=c.type||d.type,c.hl=c.lang||d.lang,c.badge=c.badge||d.badge,c.sitekey&&40===c.sitekey.length||b(),j().then(function(b){var d=b.render(a,c);return o[d]=a,d})},reload:function(a){k(),l.reset(a),e.$broadcast("reCaptchaReset",a)},execute:function(a){k(),l.execute(a)},useLang:function(a,b){var c=o[a];if(!c)throw new Error("reCaptcha Widget ID not exists",a);var d=c.querySelector("iframe");if(!b)return d&&d.src&&/[?&]hl=\w+/.test(d.src)?d.src.replace(/.+[?&]hl=(\w+)([^\w].+)?/,"$1"):null;if(d&&d.src){var e=d.src;/[?&]hl=/.test(e)?e=e.replace(/([?&]hl=)\w+/,"$1"+b):e+=(-1===e.indexOf("?")?"?":"&")+"hl="+b,d.src=e}},getResponse:function(a){return k(),l.getResponse(a)},getInstance:function(a){return o[a]},destroy:function(a){delete o[a]}}}]})}(angular),function(a){"use strict";a.module("vcRecaptcha").directive("vcRecaptcha",["$document","$timeout","vcRecaptchaService","$q",function(b,c,d,e){return{restrict:"A",require:"?^^form",scope:{response:"=?ngModel",key:"=?",stoken:"=?",theme:"=?",size:"=?",type:"=?",lang:"=?",badge:"=?",tabindex:"=?",required:"=?",onCreate:"&",onSuccess:"&",onExpire:"&"},link:function(f,g,h,i){function j(){i&&i.$setValidity("recaptcha",null),m()}function k(){c(function(){f.response="",l(),f.onExpire({widgetId:f.widgetId})})}function l(){i&&i.$setValidity("recaptcha",!1===f.required?null:Boolean(f.response))}function m(){d.destroy(f.widgetId),a.element(b[0].querySelectorAll(".pls-container")).parent().remove()}f.widgetId=null,i&&a.isDefined(h.required)&&f.$watch("required",l);var n=f.$watch("key",function(b){if(!a.isUndefined(b)&&null!==b){var i=function(a){c(function(){f.response=a,l(),f.onSuccess({response:a,widgetId:f.widgetId})})};e.resolve(b).then(function(a){return d.create(g[0],{callback:i,key:a,stoken:f.stoken||h.stoken||null,theme:f.theme||h.theme||null,type:f.type||h.type||null,lang:f.lang||h.lang||null,tabindex:f.tabindex||h.tabindex||null,size:f.size||h.size||null,badge:f.badge||h.badge||null,"expired-callback":k})}).then(function(b){l(),f.widgetId=b,f.onCreate({widgetId:b}),f.$on("$destroy",j),f.$on("reCaptchaReset",function(c,d){(a.isUndefined(d)||b===d)&&(f.response="",l())})}),n()}})}}}])}(angular);
\ No newline at end of file
diff --git a/src/directive.js b/src/directive.js
index 60b1ea9..24c9dfd 100644
--- a/src/directive.js
+++ b/src/directive.js
@@ -4,11 +4,11 @@
 
     var app = ng.module('vcRecaptcha');
 
-    app.directive('vcRecaptcha', ['$document', '$timeout', 'vcRecaptchaService', function ($document, $timeout, vcRecaptcha) {
+    app.directive('vcRecaptcha', ['$document', '$timeout', 'vcRecaptchaService', '$q', function ($document, $timeout, vcRecaptcha, $q) {
 
         return {
             restrict: 'A',
-            require: "?^^form",
+            require: '?^^form',
             scope: {
                 response: '=?ngModel',
                 key: '=?',
@@ -27,11 +27,16 @@
             link: function (scope, elm, attrs, ctrl) {
                 scope.widgetId = null;
 
-                if(ctrl && ng.isDefined(attrs.required)){
+                if (ctrl && ng.isDefined(attrs.required)) {
                     scope.$watch('required', validate);
                 }
 
                 var removeCreationListener = scope.$watch('key', function (key) {
+                    // Abort if undefined or null
+                    if (ng.isUndefined(key) || key === null) {
+                        return;
+                    }
+
                     var callback = function (gRecaptchaResponse) {
                         // Safe $apply
                         $timeout(function () {
@@ -43,19 +48,20 @@
                         });
                     };
 
-                    vcRecaptcha.create(elm[0], {
-
-                        callback: callback,
-                        key: key,
-                        stoken: scope.stoken || attrs.stoken || null,
-                        theme: scope.theme || attrs.theme || null,
-                        type: scope.type || attrs.type || null,
-                        lang: scope.lang || attrs.lang || null,
-                        tabindex: scope.tabindex || attrs.tabindex || null,
-                        size: scope.size || attrs.size || null,
-                        badge: scope.badge || attrs.badge || null,
-                        'expired-callback': expired
-
+                    // Accept a promise, or resolve immediately if the value is a bare string
+                    $q.resolve(key).then(function (resolved) {
+                        return vcRecaptcha.create(elm[0], {
+                            callback: callback,
+                            key: resolved,
+                            stoken: scope.stoken || attrs.stoken || null,
+                            theme: scope.theme || attrs.theme || null,
+                            type: scope.type || attrs.type || null,
+                            lang: scope.lang || attrs.lang || null,
+                            tabindex: scope.tabindex || attrs.tabindex || null,
+                            size: scope.size || attrs.size || null,
+                            badge: scope.badge || attrs.badge || null,
+                            'expired-callback': expired
+                        });
                     }).then(function (widgetId) {
                         // The widget has been created
                         validate();
@@ -64,13 +70,12 @@
 
                         scope.$on('$destroy', destroy);
 
-                        scope.$on('reCaptchaReset', function(event, resetWidgetId){
-                          if(ng.isUndefined(resetWidgetId) || widgetId === resetWidgetId){
-                            scope.response = "";
-                            validate();
-                          }
-                        })
-
+                        scope.$on('reCaptchaReset', function (event, resetWidgetId) {
+                            if (ng.isUndefined(resetWidgetId) || widgetId === resetWidgetId) {
+                                scope.response = '';
+                                validate();
+                            }
+                        });
                     });
 
                     // Remove this listener to avoid creating the widget more than once.
@@ -78,36 +83,36 @@
                 });
 
                 function destroy() {
-                  if (ctrl) {
-                    // reset the validity of the form if we were removed
-                    ctrl.$setValidity('recaptcha', null);
-                  }
+                    if (ctrl) {
+                        // reset the validity of the form if we were removed
+                        ctrl.$setValidity('recaptcha', null);
+                    }
 
-                  cleanup();
+                    cleanup();
                 }
 
-                function expired(){
+                function expired() {
                     // Safe $apply
                     $timeout(function () {
-                        scope.response = "";
+                        scope.response = '';
                         validate();
 
                         // Notify about the response availability
-                        scope.onExpire({ widgetId: scope.widgetId });
+                        scope.onExpire({widgetId: scope.widgetId});
                     });
                 }
 
-                function validate(){
-                    if(ctrl){
+                function validate() {
+                    if (ctrl) {
                         ctrl.$setValidity('recaptcha', scope.required === false ? null : Boolean(scope.response));
                     }
                 }
 
-                function cleanup(){
-                  vcRecaptcha.destroy(scope.widgetId);
+                function cleanup() {
+                    vcRecaptcha.destroy(scope.widgetId);
 
-                  // removes elements reCaptcha added.
-                  ng.element($document[0].querySelectorAll('.pls-container')).parent().remove();
+                    // removes elements reCaptcha added.
+                    ng.element($document[0].querySelectorAll('.pls-container')).parent().remove();
                 }
             }
         };