diff --git a/sumpy/assignment_collection.py b/sumpy/assignment_collection.py
index b44124b1c82dac3df20de820cb7fcb15a35a40c2..9a52df8e939f25c3da214a332433edb181049e56 100644
--- a/sumpy/assignment_collection.py
+++ b/sumpy/assignment_collection.py
@@ -148,7 +148,8 @@ class SymbolicAssignmentCollection(object):
         assert isinstance(name, six.string_types)
         assert name not in self.assignments
 
-        if six.PY2 and isinstance(name, unicode):
+        # coerce name onto non-unicode for Py2
+        if six.PY2 and isinstance(name, unicode):  # noqa: F821
             name = name.encode("us-ascii")
 
         if wrt_set is None: