diff --git a/pyee/base.py b/pyee/base.py
index be65c8e..99c9962 100644
--- a/pyee/base.py
+++ b/pyee/base.py
@@ -1,8 +1,8 @@
 # -*- coding: utf-8 -*-
 
-from collections import defaultdict, OrderedDict
+from collections import OrderedDict
 from threading import Lock
-from typing import Any, Callable, Dict, List, Optional, Tuple
+from typing import Any, Callable, Dict, List, Optional, Set, Tuple
 
 
 class PyeeException(Exception):
@@ -44,7 +44,7 @@ def __init__(self) -> None:
         self._events: Dict[
             str,
             "OrderedDict[Callable, Callable]",
-        ] = defaultdict(OrderedDict)
+        ] = dict()
         self._lock: Lock = Lock()
 
     def on(self, event: str, f: Optional[Callable] = None) -> Callable:
@@ -110,6 +110,8 @@ def _add_event_handler(self, event: str, k: Callable, v: Callable):
         # different for `once` handlers, where v is a wrapped version
         # of k which removes itself before calling k
         with self._lock:
+            if event not in self._events:
+                self._events[event] = OrderedDict()
             self._events[event][k] = v
 
     def _emit_run(
@@ -120,6 +122,10 @@ def _emit_run(
     ) -> None:
         f(*args, **kwargs)
 
+    def event_names(self) -> Set[str]:
+        """Get a list of events that this emitter is listening to."""
+        return set(self._events.keys())
+
     def _emit_handle_potential_error(self, event: str, error: Any) -> None:
         if event == "error":
             if isinstance(error, Exception):
@@ -136,7 +142,7 @@ def _call_handlers(
         handled = False
 
         with self._lock:
-            funcs = list(self._events[event].values())
+            funcs = list(self._events.get(event, OrderedDict()).values())
         for f in funcs:
             self._emit_run(f, args, kwargs)
             handled = True
@@ -203,6 +209,8 @@ def g(
     def _remove_listener(self, event: str, f: Callable) -> None:
         """Naked unprotected removal."""
         self._events[event].pop(f)
+        if not len(self._events[event]):
+            del self._events[event]
 
     def remove_listener(self, event: str, f: Callable) -> None:
         """Removes the function ``f`` from ``event``."""
@@ -217,7 +225,7 @@ def remove_all_listeners(self, event: Optional[str] = None) -> None:
             if event is not None:
                 self._events[event] = OrderedDict()
             else:
-                self._events = defaultdict(OrderedDict)
+                self._events = dict()
 
     def listeners(self, event: str) -> List[Callable]:
         """Returns a list of all listeners registered to the ``event``."""
diff --git a/tests/test_sync.py b/tests/test_sync.py
index 61d3dc7..e4e460c 100644
--- a/tests/test_sync.py
+++ b/tests/test_sync.py
@@ -22,6 +22,8 @@ def event_handler(data, **kwargs):
         call_me()
         assert data == "emitter is emitted!"
 
+    assert ee.event_names() == {"event"}
+
     # Making sure data is passed propers
     ee.emit("event", "emitter is emitted!", error=False)
 
@@ -43,6 +45,8 @@ def test_emit_error():
     def on_error(exc):
         call_me()
 
+    assert ee.event_names() == {"error"}
+
     # No longer raises and error instead return True indicating handled
     assert ee.emit("error", test_exception) is True
     call_me.assert_called_once()
@@ -56,6 +60,8 @@ def test_emit_return():
     call_me = Mock()
     ee = EventEmitter()
 
+    assert ee.event_names() == set()
+
     # make sure emitting without a callback returns False
     assert not ee.emit("data")
 
@@ -79,6 +85,8 @@ def test_new_listener_event():
     def event_handler(data):
         pass
 
+    assert ee.event_names() == {"new_listener", "event"}
+
     call_me.assert_called_once_with("event", event_handler)
 
 
@@ -106,6 +114,8 @@ def fourth():
 
     ee.on("event", fourth)
 
+    assert ee.event_names() == {"event"}
+
     assert ee._events["event"] == OrderedDict(
         [(first, first), (second, second), (third, third), (fourth, fourth)]
     )
@@ -120,7 +130,7 @@ def fourth():
     assert ee._events["event"] == OrderedDict([(third, third), (fourth, fourth)])
 
     ee.remove_all_listeners("event")
-    assert ee._events["event"] == OrderedDict()
+    assert "event" not in ee._events["event"]
 
 
 def test_listener_removal_on_emit():
@@ -137,6 +147,8 @@ def should_remove():
     ee.on("remove", should_remove)
     ee.on("remove", call_me)
 
+    assert ee.event_names() == {"remove"}
+
     ee.emit("remove")
 
     call_me.assert_called_once()
@@ -148,6 +160,8 @@ def should_remove():
     ee.on("remove", call_me)
     ee.on("remove", should_remove)
 
+    assert ee.event_names() == {"remove"}
+
     ee.emit("remove")
 
     call_me.assert_called_once()
@@ -169,11 +183,15 @@ def once_handler(data):
     # Tests to make sure that after event is emitted that it's gone.
     ee.once("event", once_handler)
 
+    assert ee.event_names() == {"event"}
+
     ee.emit("event", "emitter is emitted!")
 
     call_me.assert_called_once()
 
-    assert ee._events["event"] == OrderedDict()
+    assert ee.event_names() == set()
+
+    assert "event" not in ee._events
 
 
 def test_once_removal():
@@ -187,10 +205,12 @@ def once_handler(data):
     handle = ee.once("event", once_handler)
 
     assert handle == once_handler
+    assert ee.event_names() == {"event"}
 
     ee.remove_listener("event", handle)
 
-    assert ee._events["event"] == OrderedDict()
+    assert "event" not in ee._events
+    assert ee.event_names() == set()
 
 
 def test_listeners():