diff --git a/slate/slate.py b/slate/slate.py
index 3549b36..801434b 100644
--- a/slate/slate.py
+++ b/slate/slate.py
@@ -117,7 +117,7 @@ class Slate():
             if k in conf:
                 del conf[k]
 
-            if type(val, str):
+            if type(val) == str:
                 while val.find('{') != -1:
                     val = self.expand_vars(val, config=self._config, **kwargs)