diff --git a/lib/docker.js b/lib/docker.js
index 498da13..aceccd9 100644
--- a/lib/docker.js
+++ b/lib/docker.js
@@ -296,7 +296,7 @@ Docker.prototype.buildImage = function(file, opts, callback) {
     }
   }
 
-  if (file.context) {
+  if (file && file.context) {
     file.src.forEach(function(filePath) {
       content = fs.readFileSync(path.join(file.context, filePath));
       pack.entry({