diff --git a/src/docker.js b/src/docker.js
index 77e3680ca..7f53a7b78 100644
--- a/src/docker.js
+++ b/src/docker.js
@@ -76,6 +76,7 @@ function DockerError(reason, errorOrMessage) {
 }
 util.inherits(DockerError, Error);
 DockerError.INTERNAL_ERROR = 'Internal Error';
+DockerError.EXTERNAL_ERROR = 'External Error';
 DockerError.NOT_FOUND = 'Not found';
 DockerError.BAD_FIELD = 'Bad field';