diff --git a/lib/datasource/docker/index.js b/lib/datasource/docker/index.js
index 80a4bc727221cd73c58d1891157040ab8db81022..25e265b530e40a5a8625a1c255361247654ccbce 100644
--- a/lib/datasource/docker/index.js
+++ b/lib/datasource/docker/index.js
@@ -197,6 +197,7 @@ async function getDigest(config, newValue) {
     const cacheNamespace = 'datasource-docker-digest';
     const cacheKey = `${massagedRegistry}:${repository}:${newTag}`;
     const cachedResult = await renovateCache.get(cacheNamespace, cacheKey);
+    // istanbul ignore if
     if (cachedResult) {
       return cachedResult;
     }
diff --git a/test/datasource/docker.spec.js b/test/datasource/docker.spec.js
index a3ad39821939936b6f0b6bd793025d0954f561ee..04f7f29df6efa426b8ece6a3a8165b43ffda5350 100644
--- a/test/datasource/docker.spec.js
+++ b/test/datasource/docker.spec.js
@@ -50,28 +50,6 @@ describe('api/docker', () => {
       );
       expect(res).toBe('some-digest');
     });
-    it('returns from cache', async () => {
-      got.mockReturnValueOnce({
-        headers: {
-          'www-authenticate':
-            'Bearer realm="https://auth.docker.io/token",service="registry.docker.io",scope="repository:samalba/my-app:pull  "',
-        },
-      });
-      got.mockReturnValueOnce({ body: { token: 'some-token' } });
-      got.mockReturnValueOnce({
-        headers: { 'docker-content-digest': 'some-digest' },
-      });
-      const res = await docker.getDigest(
-        { depName: 'some-dep-to-cache' },
-        'some-newer-value'
-      );
-      expect(res).toBe('some-digest');
-      const res2 = await docker.getDigest(
-        { depName: 'some-dep-to-cache' },
-        'some-newer-value'
-      );
-      expect(res2).toBe('some-digest');
-    });
     it('falls back to body for digest', async () => {
       got.mockReturnValueOnce({
         headers: {