diff --git a/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js b/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
index 550c9b2b37..8ec39c5887 100644
--- a/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
+++ b/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
@@ -1,6 +1,5 @@
 const should = require('should');
 const sinon = require('sinon');
-const Promise = require('bluebird');
 const CachedImageSizeFromUrl = require('../../../../../core/server/lib/image/cached-image-size-from-url');
 
 describe('lib/image: image size cache', function () {
@@ -15,16 +14,15 @@ describe('lib/image: image size cache', function () {
         sinon.restore();
     });
 
-    it('should read from cache, if dimensions for image are fetched already', function (done) {
+    it('should read from cache, if dimensions for image are fetched already', async function () {
         const url = 'http://mysite.com/content/image/mypostcoverimage.jpg';
-        let cachedImagedSizeResult;
         let imageSizeSpy;
 
-        sizeOfStub.returns(new Promise.resolve({
+        sizeOfStub.resolves({
             width: 50,
             height: 50,
             type: 'jpg'
-        }));
+        });
 
         const cachedImageSizeFromUrl = new CachedImageSizeFromUrl({
             imageSize: {
@@ -35,41 +33,37 @@ describe('lib/image: image size cache', function () {
 
         imageSizeSpy = sizeOfStub;
 
-        cachedImagedSizeResult = Promise.resolve(cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url));
-        cachedImagedSizeResult.then(function () {
-            // first call to get result from `getImageSizeFromUrl`
-            cachedImagedSize = cachedImageSizeFromUrl.cache;
-            should.exist(cachedImagedSize);
-            cachedImagedSize.has(url).should.be.true;
-            const image = cachedImagedSize.get(url);
-            should.exist(image.width);
-            image.width.should.be.equal(50);
-            should.exist(image.height);
-            image.height.should.be.equal(50);
+        await cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url);
 
-            // second call to check if values get returned from cache
-            cachedImagedSizeResult = Promise.resolve(cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url));
-            cachedImagedSizeResult.then(function () {
-                imageSizeSpy.calledOnce.should.be.true();
-                imageSizeSpy.calledTwice.should.be.false();
-                cachedImagedSize = cachedImageSizeFromUrl.cache;
-                should.exist(cachedImagedSize);
-                cachedImagedSize.has(url).should.be.true;
-                const image2 = cachedImagedSize.get(url);
-                should.exist(image2.width);
-                image2.width.should.be.equal(50);
-                should.exist(image2.height);
-                image2.height.should.be.equal(50);
-                done();
-            });
-        }).catch(done);
+        // first call to get result from `getImageSizeFromUrl`
+        cachedImagedSize = cachedImageSizeFromUrl.cache;
+        should.exist(cachedImagedSize);
+        cachedImagedSize.has(url).should.be.true;
+        const image = cachedImagedSize.get(url);
+        should.exist(image.width);
+        image.width.should.be.equal(50);
+        should.exist(image.height);
+        image.height.should.be.equal(50);
+
+        // second call to check if values get returned from cache
+        await cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url);
+
+        imageSizeSpy.calledOnce.should.be.true();
+        imageSizeSpy.calledTwice.should.be.false();
+        cachedImagedSize = cachedImageSizeFromUrl.cache;
+        should.exist(cachedImagedSize);
+        cachedImagedSize.has(url).should.be.true;
+        const image2 = cachedImagedSize.get(url);
+        should.exist(image2.width);
+        image2.width.should.be.equal(50);
+        should.exist(image2.height);
+        image2.height.should.be.equal(50);
     });
 
-    it('can handle image-size errors', function (done) {
+    it('can handle image-size errors', async function () {
         const url = 'http://mysite.com/content/image/mypostcoverimage.jpg';
-        let cachedImageSizeResult;
 
-        sizeOfStub.returns(new Promise.reject('error'));
+        sizeOfStub.rejects('error');
 
         const cachedImageSizeFromUrl = new CachedImageSizeFromUrl({
             imageSize: {
@@ -78,19 +72,17 @@ describe('lib/image: image size cache', function () {
             cache: new Map()
         });
 
-        cachedImageSizeResult = Promise.resolve(cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url));
-        cachedImageSizeResult.then(function () {
-            cachedImagedSize = cachedImageSizeFromUrl.cache;
-            should.exist(cachedImagedSize);
-            cachedImagedSize.has(url).should.be.true;
-            const image = cachedImagedSize.get(url);
-            should.not.exist(image.width);
-            should.not.exist(image.height);
-            done();
-        }).catch(done);
+        await cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url);
+
+        cachedImagedSize = cachedImageSizeFromUrl.cache;
+        should.exist(cachedImagedSize);
+        cachedImagedSize.has(url).should.be.true;
+        const image = cachedImagedSize.get(url);
+        should.not.exist(image.width);
+        should.not.exist(image.height);
     });
 
-    it('should return null if url is undefined', function (done) {
+    it('should return null if url is undefined', async function () {
         const cachedImageSizeFromUrl = new CachedImageSizeFromUrl({
             imageSize: {},
             cache: new Map()
@@ -98,9 +90,8 @@ describe('lib/image: image size cache', function () {
         const url = null;
         let result;
 
-        result = cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url);
+        result = await cachedImageSizeFromUrl.getCachedImageSizeFromUrl(url);
 
         should.not.exist(result);
-        done();
     });
 });