diff --git a/src/docker.js b/src/docker.js
index 962721c8b..37fcb4422 100644
--- a/src/docker.js
+++ b/src/docker.js
@@ -110,14 +110,16 @@ async function getAuthConfig(image) {
     return autoConfig;
 }
 
-async function pullImage(manifest) {
-    const authConfig = await getAuthConfig(manifest.dockerImage);
+async function pullImage(dockerImage) {
+    assert.strictEqual(typeof dockerImage, 'string');
 
-    debug(`pullImage: will pull ${manifest.dockerImage}. auth: ${authConfig ? 'yes' : 'no'}`);
+    const authConfig = await getAuthConfig(dockerImage);
 
-    const [error, stream] = await safe(gConnection.pull(manifest.dockerImage, { authconfig: authConfig }));
-    if (error && error.statusCode === 404) throw new BoxError(BoxError.NOT_FOUND, `Unable to pull image ${manifest.dockerImage}. message: ${error.message} statusCode: ${error.statusCode}`);
-    if (error) throw new BoxError(BoxError.DOCKER_ERROR, `Unable to pull image ${manifest.dockerImage}. Please check the network or if the image needs authentication. statusCode: ${error.statusCode}`);
+    debug(`pullImage: will pull ${dockerImage}. auth: ${authConfig ? 'yes' : 'no'}`);
+
+    const [error, stream] = await safe(gConnection.pull(dockerImage, { authconfig: authConfig }));
+    if (error && error.statusCode === 404) throw new BoxError(BoxError.NOT_FOUND, `Unable to pull image ${dockerImage}. message: ${error.message} statusCode: ${error.statusCode}`);
+    if (error) throw new BoxError(BoxError.DOCKER_ERROR, `Unable to pull image ${dockerImage}. Please check the network or if the image needs authentication. statusCode: ${error.statusCode}`);
 
     return new Promise((resolve, reject) => {
         // https://github.com/dotcloud/docker/issues/1074 says each status message is emitted as a chunk
@@ -128,13 +130,13 @@ async function pullImage(manifest) {
 
             // The data.status here is useless because this is per layer as opposed to per image
             if (!data.status && data.error) { // data is { errorDetail: { message: xx } , error: xx }
-                debug(`pullImage error ${manifest.dockerImage}: ${data.errorDetail.message}`);
+                debug(`pullImage error ${dockerImage}: ${data.errorDetail.message}`);
                 layerError = data.errorDetail;
             }
         });
 
         stream.on('end', function () {
-            debug(`downloaded image ${manifest.dockerImage} . error: ${!!layerError}`);
+            debug(`downloaded image ${dockerImage} . error: ${!!layerError}`);
 
             if (!layerError) return resolve();
 
@@ -142,7 +144,7 @@ async function pullImage(manifest) {
         });
 
         stream.on('error', function (error) { // this is only hit for stream error and not for some download error
-            debug('error pulling image %s: %o', manifest.dockerImage, error);
+            debug(`error pulling image ${dockerImage}: %o`, error);
             reject(new BoxError(BoxError.DOCKER_ERROR, error.message));
         });
     });
@@ -159,7 +161,7 @@ async function downloadImage(manifest) {
     if (!error && result) return; // image is already present locally
 
     await promiseRetry({ times: 10, interval: 5000, debug, retry: (pullError) => pullError.reason !== BoxError.NOT_FOUND && pullError.reason !== BoxError.FS_ERROR }, async () => {
-        await pullImage(manifest);
+        await pullImage(manifest.dockerImage);
     });
 }