tweak references error message
diff --git a/reclass/datatypes/parameters.py b/reclass/datatypes/parameters.py
index 29ab5b6..f9210c7 100644
--- a/reclass/datatypes/parameters.py
+++ b/reclass/datatypes/parameters.py
@@ -308,4 +308,4 @@
                 old = len(value.get_references())
                 value.assembleRefs(self._base)
                 if old == len(value.get_references()):
-                    raise InterpolationError('Missing references: {0}, for path: {1}'.format(value.get_references(), str(path)))
+                    raise InterpolationError('Bad references: {0}, for path: {1}'.format(value.get_references(), str(path)))
diff --git a/reclass/datatypes/tests/test_parameters.py b/reclass/datatypes/tests/test_parameters.py
index 8369ae5..0e8de3b 100644
--- a/reclass/datatypes/tests/test_parameters.py
+++ b/reclass/datatypes/tests/test_parameters.py
@@ -501,7 +501,7 @@
         p1 = Parameters({'alpha': {'one': 1, 'two': 2}, 'gamma': '${alpha:${beta}}'})
         with self.assertRaises(InterpolationError) as error:
             p1.interpolate()
-        self.assertEqual(error.exception.message, "Missing references: ['beta'], for path: gamma")
+        self.assertEqual(error.exception.message, "Bad references: ['beta'], for path: gamma")
 
 if __name__ == '__main__':
     unittest.main()