diff --git a/.gitignore b/.gitignore
index 1b019739..b7e3188b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@ config.yaml
 registration.yaml
 *.db
 *.session
+*.json
diff --git a/mautrix_appservice/appservice.py b/mautrix_appservice/appservice.py
index 8a25e5e9..0b66d57b 100644
--- a/mautrix_appservice/appservice.py
+++ b/mautrix_appservice/appservice.py
@@ -34,7 +34,8 @@ class AppService:
         self.as_token = as_token
         self.hs_token = hs_token
         self.bot_mxid = f"@{bot_localpart}:{domain}"
-        self.state_store = StateStore()
+        self.state_store = StateStore(autosave_file="mx-state.json")
+        self.state_store.load("mx-state.json")
 
         self.transactions = []
 
diff --git a/mautrix_appservice/intent_api.py b/mautrix_appservice/intent_api.py
index 9de0bbeb..aa8b322c 100644
--- a/mautrix_appservice/intent_api.py
+++ b/mautrix_appservice/intent_api.py
@@ -152,7 +152,6 @@ class IntentAPI:
         self.localpart = results.group(1)
 
         self.state_store = state_store
-        self.registered = False
 
     def user(self, user):
         if not self.bot:
@@ -336,15 +335,16 @@ class IntentAPI:
                 raise IntentError(f"Failed to join room {room_id} as {self.mxid}", e2)
 
     def _ensure_registered(self):
-        if self.registered:
+        if self.state_store.is_registered(self.mxid):
             return
         try:
             self.client.register({"username": self.localpart})
         except MatrixRequestError as e:
             if matrix_error_code(e) != "M_USER_IN_USE":
                 self.log.exception(f"Failed to register {self.mxid}!")
+                return
                 # raise IntentError(f"Failed to register {self.mxid}", e)
-        self.registered = True
+        self.state_store.registered(self.mxid)
 
     def _ensure_has_power_level_for(self, room_id, event_type):
         if not self.state_store.has_power_level_data(room_id):
diff --git a/mautrix_appservice/state_store.py b/mautrix_appservice/state_store.py
index bdfa211a..decc35d5 100644
--- a/mautrix_appservice/state_store.py
+++ b/mautrix_appservice/state_store.py
@@ -14,11 +14,61 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+import json
+
 
 class StateStore:
-    def __init__(self):
+    def __init__(self, autosave_file=None):
+        self.registrations = set()
         self.memberships = {}
         self.power_levels = {}
+        self.autosave_file = autosave_file
+
+    def save(self, file):
+        if isinstance(file, str):
+            output = open(file, "w")
+        else:
+            output = file
+
+        json.dump({
+            "registrations": list(self.registrations),
+            "memberships": self.memberships,
+            "power_levels": self.power_levels,
+        }, output)
+
+        if isinstance(file, str):
+            output.close()
+
+    def load(self, file):
+        if isinstance(file, str):
+            try:
+                input = open(file, "r")
+            except FileNotFoundError:
+                return
+        else:
+            input = file
+
+        data = json.load(input)
+        if "registrations" in data:
+            self.registrations = set(data["registrations"])
+        if "memberships" in data:
+            self.memberships = data["memberships"]
+        if "power_levels" in data:
+            self.power_levels = data["power_levels"]
+
+        if isinstance(file, str):
+            input.close()
+
+    def _autosave(self):
+        if self.autosave_file:
+            self.save(self.autosave_file)
+
+    def is_registered(self, user):
+        return user in self.registrations
+
+    def registered(self, user):
+        self.registrations.add(user)
+        self._autosave()
 
     def _get_membership(self, room, user):
         return self.memberships.get(room, {}).get(user, "left")
@@ -30,6 +80,7 @@ class StateStore:
         if room not in self.memberships:
             self.memberships[room] = {}
         self.memberships[room][user] = membership
+        self._autosave()
 
     def joined(self, room, user):
         return self._set_membership(room, user, "join")
@@ -56,6 +107,7 @@ class StateStore:
                 "events": {},
             }
         self.power_levels[room]["users"][user] = level
+        self._autosave()
 
     def set_power_levels(self, room, content):
         if "events" not in content:
@@ -63,3 +115,4 @@ class StateStore:
         if "users" not in content:
             content["users"] = {}
         self.power_levels[room] = content
+        self._autosave()