diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index d48e0d00..63b954af 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -125,6 +125,7 @@ export class Session {
             olmEncryption: this._olmEncryption,
             megolmEncryption: this._megolmEncryption,
             megolmDecryption: this._megolmDecryption,
+            storage: this._storage,
             encryptionParams
         });
     }
diff --git a/src/matrix/e2ee/RoomEncryption.js b/src/matrix/e2ee/RoomEncryption.js
index cd918292..3538381f 100644
--- a/src/matrix/e2ee/RoomEncryption.js
+++ b/src/matrix/e2ee/RoomEncryption.js
@@ -128,6 +128,22 @@ export class RoomEncryption {
         };
     }
 
+    needsToShareKeys(memberChanges) {
+        for (const m of memberChanges.values()) {
+            if (m.member.needsRoomKey) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    async shareRoomKeyToPendingMembers(hsApi) {
+        // sucks to call this for all encrypted rooms on startup?
+        const txn = await this._storage.readTxn([this._storage.storeNames.roomMembers]);
+        const pendingUserIds = await txn.roomMembers.getUserIdsNeedingRoomKey(this._room.id);
+        return await this._shareRoomKey(pendingUserIds, hsApi);
+    }
+
     async shareRoomKeyForMemberChanges(memberChanges, hsApi) {
         const pendingUserIds = [];
         for (const m of memberChanges.values()) {
diff --git a/src/matrix/room/Room.js b/src/matrix/room/Room.js
index b4e19a80..55bb1ccb 100644
--- a/src/matrix/room/Room.js
+++ b/src/matrix/room/Room.js
@@ -157,7 +157,8 @@ export class Room extends EventEmitter {
             newLiveKey,
             removedPendingEvents,
             memberChanges,
-            heroChanges
+            heroChanges,
+            needsAfterSyncCompleted: this._roomEncryption?.needsToShareKeys(memberChanges)
         };
     }
 
@@ -204,6 +205,17 @@ export class Room extends EventEmitter {
         }
 	}
 
+    /**
+     * Only called if the result of writeSync had `needsAfterSyncCompleted` set.
+     * Can be used to do longer running operations that resulted from the last sync,
+     * like network operations.
+     */
+    async afterSyncCompleted({memberChanges}) {
+        if (this._roomEncryption) {
+            await this._roomEncryption.shareRoomKeyForMemberChanges(memberChanges, this._hsApi);
+        }
+    }
+
     /** @package */
     resumeSending() {
         this._sendQueue.resumeSending();
diff --git a/src/matrix/storage/idb/QueryTarget.js b/src/matrix/storage/idb/QueryTarget.js
index fd3050bd..6d11932f 100644
--- a/src/matrix/storage/idb/QueryTarget.js
+++ b/src/matrix/storage/idb/QueryTarget.js
@@ -187,6 +187,14 @@ export class QueryTarget {
         return results;
     }
 
+    async iterateWhile(range, predicate) {
+        const cursor = this._openCursor(range, "next");
+        await iterateCursor(cursor, (value) => {
+            const passesPredicate = predicate(value);
+            return {done: !passesPredicate};
+        });
+    }
+
     async _find(range, predicate, direction) {
         const cursor = this._openCursor(range, direction);
         let result;
diff --git a/src/matrix/storage/idb/stores/RoomMemberStore.js b/src/matrix/storage/idb/stores/RoomMemberStore.js
index be2b16ec..6d354dd9 100644
--- a/src/matrix/storage/idb/stores/RoomMemberStore.js
+++ b/src/matrix/storage/idb/stores/RoomMemberStore.js
@@ -60,4 +60,19 @@ export class RoomMemberStore {
         });
         return userIds;
     }
+
+    async getUserIdsNeedingRoomKey(roomId) {
+        const userIds = [];
+        const range = IDBKeyRange.lowerBound(encodeKey(roomId, ""));
+        await this._roomMembersStore.iterateWhile(range, member => {
+            if (member.roomId !== roomId) {
+                return false;
+            }
+            if (member.needsRoomKey) {
+                userIds.push(member.userId);
+            }
+            return true;
+        });
+        return userIds;
+    }
 }