diff --git a/lib/carto/external.js b/lib/carto/external.js
index 7cb0ffa..49ca6ac 100644
--- a/lib/carto/external.js
+++ b/lib/carto/external.js
@@ -124,6 +124,8 @@ External.prototype.findOneByExtension = function(ext, callback) {
     this.findByExtension(ext, cb);
 }
 
+// Find a file by extension in `this.path()`.
+// Ignores .directories and .files
 External.prototype.findByExtension = function(ext, callback) {
     var running = 0;
     var found = [];
@@ -138,6 +140,8 @@ External.prototype.findByExtension = function(ext, callback) {
                 i;
             }
             files.forEach(function(file) {
+                // Ignore dotfiles and dot-directories
+                if (file[0] === '.') return;
                 running++;
                 file = path.join(dir, file);
                 fs.stat(file, function(err, stats) {
diff --git a/test/external.test.js b/test/external.test.js
index fb606db..2c3f1f4 100644
--- a/test/external.test.js
+++ b/test/external.test.js
@@ -75,3 +75,13 @@ exports['test External with remote KML file'] = function(beforeExit) {
             helper.md5File(external.path(), 'f8aea6d693a48dabdc7ea3586cce57f7', context);
         });
 };
+
+exports['test External with DS_Store'] = function(beforeExit) {
+    new External(env, 'http://tilemill-testing.s3.amazonaws.com/carto/station_circles_bad.zip')
+        .on('complete', function(external) {
+            assert.ok(external instanceof External);
+            external.findDataFile(function(err, file) {
+                assert.eql('station_circles.shp', path.basename(file), 'The non-dot file was chosen');
+            });
+        });
+};