diff --git a/pubspec.yaml b/pubspec.yaml
index 2cd3aee..ac3bbe3 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -6,4 +6,4 @@
 environment:
   sdk: '>=1.0.0 <2.0.0'
 dev_dependencies:
-  unittest: ">=0.9.0 <0.10.0"
+  unittest: ">=0.9.0 <0.12.0"
diff --git a/test/mustache_specs.dart b/test/mustache_specs.dart
index a2287a7..c55e376 100644
--- a/test/mustache_specs.dart
+++ b/test/mustache_specs.dart
@@ -29,11 +29,13 @@
   var specs_dir = new Directory('test/spec/specs');
   specs_dir
     .listSync()
-    .forEach((File f) {
-      var filename = f.path;
-      if (shouldRun(filename)) {
-        var text = f.readAsStringSync(encoding: UTF8);
-        _defineGroupFromFile(filename, text);
+    .forEach((f) {
+      if (f is File) {
+        var filename = f.path;
+        if (shouldRun(filename)) {
+          var text = f.readAsStringSync(encoding: UTF8);
+          _defineGroupFromFile(filename, text);
+        }
       }
     });
 }