diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 49b3255..d6bd9e1 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -1,9 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ChangeListManager">
-    <list default="true" id="90d8ba04-9050-43ac-b510-29c92d20abe1" name="Default" comment="">
-      <change type="MODIFICATION" beforePath="$PROJECT_DIR$/src/index.js" afterPath="$PROJECT_DIR$/src/index.js" />
-    </list>
+    <list default="true" id="90d8ba04-9050-43ac-b510-29c92d20abe1" name="Default" comment="" />
     <ignored path="psd-simpledi.iws" />
     <ignored path=".idea/workspace.xml" />
     <option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
@@ -27,7 +25,7 @@
         <entry file="file://$PROJECT_DIR$/src/index.js">
           <provider selected="true" editor-type-id="text-editor">
             <state vertical-scroll-proportion="0.8302425">
-              <caret line="118" column="3" selection-start-line="118" selection-start-column="3" selection-end-line="118" selection-end-column="3" />
+              <caret line="116" column="3" selection-start-line="116" selection-start-column="3" selection-end-line="116" selection-end-column="3" />
               <folding />
             </state>
           </provider>
@@ -59,22 +57,12 @@
             <state vertical-scroll-proportion="0.0">
               <caret line="9" column="45" selection-start-line="9" selection-start-column="45" selection-end-line="9" selection-end-column="45" />
               <folding>
-                <marker date="1442495151000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
+                <marker date="1442497802000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
               </folding>
             </state>
           </provider>
         </entry>
       </file>
-      <file leaf-file-name="polyfill.js" pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/dist/polyfill.js">
-          <provider selected="true" editor-type-id="text-editor">
-            <state vertical-scroll-proportion="0.0">
-              <caret line="130" column="35" selection-start-line="130" selection-start-column="35" selection-end-line="130" selection-end-column="35" />
-              <folding />
-            </state>
-          </provider>
-        </entry>
-      </file>
       <file leaf-file-name="index.js" pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/dist/index.js">
           <provider selected="true" editor-type-id="text-editor">
@@ -580,19 +568,11 @@
         <state vertical-scroll-proportion="0.0">
           <caret line="9" column="45" selection-start-line="9" selection-start-column="45" selection-end-line="9" selection-end-column="45" />
           <folding>
-            <marker date="1442495151000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
+            <marker date="1442497802000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
           </folding>
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/dist/polyfill.js">
-      <provider selected="true" editor-type-id="text-editor">
-        <state vertical-scroll-proportion="0.0">
-          <caret line="130" column="35" selection-start-line="130" selection-start-column="35" selection-end-line="130" selection-end-column="35" />
-          <folding />
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/dist/index.js">
       <provider selected="true" editor-type-id="text-editor">
         <state vertical-scroll-proportion="0.0">
@@ -665,7 +645,7 @@
         <state vertical-scroll-proportion="0.0">
           <caret line="6" column="33" selection-start-line="6" selection-start-column="33" selection-end-line="6" selection-end-column="33" />
           <folding>
-            <marker date="1442495151000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
+            <marker date="1442497802000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
           </folding>
         </state>
       </provider>
@@ -761,19 +741,11 @@
         <state vertical-scroll-proportion="0.0">
           <caret line="9" column="45" selection-start-line="9" selection-start-column="45" selection-end-line="9" selection-end-column="45" />
           <folding>
-            <marker date="1442495151000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
+            <marker date="1442497802000" expanded="true" signature="167:493" placeholder="{&quot;prepublish&quot;: &quot;npm run bundle&quot;...}" />
           </folding>
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/dist/polyfill.js">
-      <provider selected="true" editor-type-id="text-editor">
-        <state vertical-scroll-proportion="0.0">
-          <caret line="130" column="35" selection-start-line="130" selection-start-column="35" selection-end-line="130" selection-end-column="35" />
-          <folding />
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/dist/index.js">
       <provider selected="true" editor-type-id="text-editor">
         <state vertical-scroll-proportion="0.0">
@@ -820,7 +792,7 @@
     <entry file="file://$PROJECT_DIR$/src/index.js">
       <provider selected="true" editor-type-id="text-editor">
         <state vertical-scroll-proportion="0.8302425">
-          <caret line="118" column="3" selection-start-line="118" selection-start-column="3" selection-end-line="118" selection-end-column="3" />
+          <caret line="116" column="3" selection-start-line="116" selection-start-column="3" selection-end-line="116" selection-end-column="3" />
           <folding />
         </state>
       </provider>
diff --git a/dist/index.js b/dist/index.js
index eea5324..0ff9c05 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -149,14 +149,16 @@ var Scorpion = (function () {
   }, {
     key: 'once',
     value: function once(factory) {
-      var _arguments = arguments;
-
       var id = (0, _utils.uuid)();
       return function () {
+        for (var _len4 = arguments.length, args = Array(_len4), _key4 = 0; _key4 < _len4; _key4++) {
+          args[_key4] = arguments[_key4];
+        }
+
         if (!_instanceCache[id]) {
           var thisArg = {};
           _instanceCache[id] = {
-            returnValue: factory.apply(thisArg, _arguments)
+            returnValue: factory.apply(thisArg, args)
           };
         }
         return _instanceCache[id].returnValue;
diff --git a/package.json b/package.json
index 724cd5b..ce11da4 100644
--- a/package.json
+++ b/package.json
@@ -47,5 +47,5 @@
     "prepublish": "npm run bundle",
     "test": "mocha --reporter dot --recursive -r setup-referee-sinon/globals test/unit --compilers js:babel/register"
   },
-  "version": "1.0.3"
+  "version": "1.0.4"
 }
diff --git a/src/index.js b/src/index.js
index 8cdddd2..3bcb75b 100644
--- a/src/index.js
+++ b/src/index.js
@@ -105,11 +105,11 @@ export default class Scorpion {
 
   static once(factory) {
     const id = uuid();
-    return () => {
+    return (...args) => {
       if (!_instanceCache[id]) {
         const thisArg = {};
         _instanceCache[id] = {
-          returnValue: factory.apply(thisArg, arguments)
+          returnValue: factory.apply(thisArg, args)
         };
       }
       return _instanceCache[id].returnValue;
diff --git a/test/unit/index-spec.js b/test/unit/index-spec.js
index 19002f9..a9fbcfc 100644
--- a/test/unit/index-spec.js
+++ b/test/unit/index-spec.js
@@ -76,29 +76,27 @@ describe('Scorpion', function() {
       });
     });
 
-    it('retrieves a module', function(done) {
-      di.get('depA').then(function(retrievedObj) {
+    it('retrieves a module', function() {
+      return di.get('depA').then(function(retrievedObj) {
         expect(retrievedObj).toBe(depA);
-        done();
       });
     });
 
-    it('retrieves an async module', function(done) {
-      di.get('depB').then(function(retrievedObj) {
+    it('retrieves an async module', function() {
+      return di.get('depB').then(function(retrievedObj) {
         expect(retrievedObj).toBe(depB);
-        done();
       });
     });
 
-    it('retrieves an async module and resolves its dependencies', function(done) {
+    it('retrieves an async module and resolves its dependencies', function() {
       di.register('depC', ['depB'], function(dependencyB) {
         return new Promise(function(resolve) {
           resolve([depC, dependencyB]);
         });
       });
-      di.get('depC').then(function(arr) {
+      return di.get('depC').then(function(arr) {
         expect(arr).toEqual([depC, depB]);
-      }).then(done, done);
+      });
     });
 
     it('throws when trying to resolve a direct cicular dependency', function() {
@@ -160,32 +158,30 @@ describe('Scorpion', function() {
   });
 
   describe('Scorpion.withNew', function() {
-    it('initializes a Constructor with new', function(done) {
+    it('initializes a Constructor with new', function() {
       class Foo {
         bar() {}
       }
 
       di.register('Foo', Scorpion.withNew(Foo));
 
-      di.get('Foo').then(function(foo) {
+      return di.get('Foo').then(function(foo) {
         expect(foo instanceof Foo);
         expect(foo.bar).not.toBe(undefined);
-        done();
       });
     });
   });
 
   describe('Scorpion.withNewOnce', function() {
-    it('initializes a constructor with new once and then always returns the instance', function(done) {
+    it('initializes a constructor with new once and then always returns the instance', function() {
       function Foo() {
         this.foo = true;
       }
 
       di.register('Foo', Scorpion.withNewOnce(Foo));
 
-      Promise.all([di.get('Foo'), di.get('Foo')]).then((values) => {
+      return Promise.all([di.get('Foo'), di.get('Foo')]).then((values) => {
         expect(values[0]).toBe(values[1]);
-        done();
       });
     });
 
@@ -209,13 +205,21 @@ describe('Scorpion', function() {
   });
 
   describe('Scorpion.once', function() {
-    it('calls the factory once even when get is called multiple times', function(done) {
+    it('calls the factory once even when get is called multiple times', function() {
       const spy = sinon.spy();
       di.register('foo', Scorpion.once(spy));
 
-      Promise.all([di.get('foo'), di.get('foo')]).then(function() {
+      return Promise.all([di.get('foo'), di.get('foo')]).then(function() {
         expect(spy.calledOnce).toBe(true);
-        done();
+      });
+    });
+    it('forwards the defined dependencies to the passed factory', function() {
+      const spy = sinon.spy();
+      di.register('bar', Scorpion.always('bar'));
+      di.register('foo', ['bar'], Scorpion.once(spy));
+
+      return di.get('foo').then(function(bar) {
+        expect(spy).toHaveBeenCalledWith('bar');
       });
     });
   });