diff --git a/tests/test_enum.py b/tests/test_enum.py
index b8a3b71c..dcc549dd 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -105,6 +105,22 @@ def goodbye(self):
         assert s.is_ONE()
         assert s.message == 'Goodbye'
 
+    def test_str_enum(self):
+        class States(str, enum.Enum):
+            ONE = "one"
+            TWO = "two"
+
+        class Stuff(object):
+            def __init__(self, machine_cls):
+                self.state = None
+                self.machine = machine_cls(states=States, initial=States.ONE, model=self)
+                self.machine.add_transition("advance", States.ONE, States.TWO)
+
+        s = Stuff(self.machine_cls)
+        assert s.is_ONE()
+        s.advance()
+        assert s.is_TWO()
+
 
 @skipIf(enum is None, "enum is not available")
 class TestNestedStateEnums(TestEnumsAsStates):
diff --git a/transitions/core.py b/transitions/core.py
index 0a44f764..15dad6f0 100644
--- a/transitions/core.py
+++ b/transitions/core.py
@@ -858,7 +858,7 @@ def add_transition(self, trigger, source, dest, conditions=None,
             for model in self.models:
                 self._add_trigger_to_model(trigger, model)
 
-        if isinstance(source, string_types):
+        if isinstance(source, string_types) and not isinstance(source, Enum):
             source = list(self.states.keys()) if source == self.wildcard_all else [source]
         else:
             source = [s.name if self._has_state(s) or isinstance(s, Enum) else s for s in listify(source)]