diff --git a/conda_env/specs/requirements.py b/conda_env/specs/requirements.py
index 9d30e758de6..cf56aacd0fa 100644
--- a/conda_env/specs/requirements.py
+++ b/conda_env/specs/requirements.py
@@ -12,7 +12,7 @@ class RequirementsSpec(object):
     and returns an Environment object from it.
     '''
     msg = None
-    extensions = set(['.txt',])
+    extensions = set(['.txt', ])
 
     def __init__(self, filename=None, name=None, **kwargs):
         self.filename = filename