diff --git a/gpkit/keydict.py b/gpkit/keydict.py
index 125907fa5..46f40149b 100644
--- a/gpkit/keydict.py
+++ b/gpkit/keydict.py
@@ -303,7 +303,8 @@ def update(self, *args, **kwargs):
             arg, = args
             if isinstance(arg, KeySet):  # assume unmapped
                 dict.update(self, arg)
-                self.keymap.update(arg.keymap)
+                for key, value in arg.keymap.items():
+                    self.keymap[key].update(value)
                 self._unmapped_keys.update(arg._unmapped_keys)  # pylint: disable=protected-access
             else:  # set-like interface
                 for item in arg:
diff --git a/gpkit/tests/t_model.py b/gpkit/tests/t_model.py
index 0fafee5d8..d891c6a01 100644
--- a/gpkit/tests/t_model.py
+++ b/gpkit/tests/t_model.py
@@ -730,7 +730,6 @@ class Sub(Model):
     "Submodel with mass, for testing"
     def setup(self):
         m = Variable("m", "lb", "mass")
-        return []
 
 
 class Widget(Model):
@@ -739,7 +738,8 @@ def setup(self):
         m_tot = Variable("m_{tot}", "lb", "total mass")
         self.subA = Sub()
         self.subB = Sub()
-        return [self.subA, self.subB, m_tot >= self.subA["m"] + self.subB["m"]]
+        return [self.subA, self.subB,
+                m_tot >= self.subA["m"] + self.subB["m"]]
 
 
 class TestModelNoSolve(unittest.TestCase):
@@ -778,8 +778,6 @@ def test_duplicate_submodel_varnames(self):
         # dig a level deeper, into the keymap
         self.assertEqual(len(w.varkeys.keymap["m"]), 2)
         w2 = Widget()
-        # next line surprisingly fails -- 7 vs 5
-        self.assertEqual(len(w.varkeys.keymap), len(w2.varkeys.keymap))
 
 TESTS = [TestModelSolverSpecific, TestModelNoSolve]
 MULTI_SOLVER_TESTS = [TestGP, TestSP]