diff --git a/slate/slate.py b/slate/slate.py
index 0e9b902..bca09b8 100644
--- a/slate/slate.py
+++ b/slate/slate.py
@@ -104,9 +104,10 @@ class Slate():
     def expand_vars(self, string, delta_desc='BASE', **kwargs):
         if isinstance(string, str):
             rand = int(random.random()*99999999)
+            tmp = os.path.expandvars('$TMP')
             if string == '{rand}':
                 return rand
-            return string.format(delta_desc=delta_desc, **kwargs, rand=rand)
+            return string.format(delta_desc=delta_desc, **kwargs, rand=rand, tmp=tmp)
         return string
 
     def apply_nested(self, d, f):