diff --git a/homeassistant/components/recorder/models.py b/homeassistant/components/recorder/models.py
index 6e3e2db064d..671623ec564 100644
--- a/homeassistant/components/recorder/models.py
+++ b/homeassistant/components/recorder/models.py
@@ -92,7 +92,8 @@ class States(Base):   # type: ignore
         else:
             dbstate.domain = state.domain
             dbstate.state = state.state
-            dbstate.attributes = json.dumps(dict(state.attributes))
+            dbstate.attributes = json.dumps(dict(state.attributes),
+                                            cls=JSONEncoder)
             dbstate.last_changed = state.last_changed
             dbstate.last_updated = state.last_updated