diff --git a/changelog.d/4113.bugfix b/changelog.d/4113.bugfix
new file mode 100644
index 000000000000..7f9d8ee0326a
--- /dev/null
+++ b/changelog.d/4113.bugfix
@@ -0,0 +1 @@
+Fix e2e key backup with more than 9 backup versions
diff --git a/synapse/storage/e2e_room_keys.py b/synapse/storage/e2e_room_keys.py
index f25ded229520..16b7f005aa9a 100644
--- a/synapse/storage/e2e_room_keys.py
+++ b/synapse/storage/e2e_room_keys.py
@@ -118,6 +118,11 @@ def get_e2e_room_keys(
             these room keys.
         """
 
+        try:
+            version = int(version)
+        except ValueError:
+            defer.returnValue({'rooms': {}})
+
         keyvalues = {
             "user_id": user_id,
             "version": version,
@@ -212,14 +217,23 @@ def get_e2e_room_keys_version_info(self, user_id, version=None):
         Raises:
             StoreError: with code 404 if there are no e2e_room_keys_versions present
         Returns:
-            A deferred dict giving the info metadata for this backup version
+            A deferred dict giving the info metadata for this backup version, with
+            fields including:
+                version(str)
+                algorithm(str)
+                auth_data(object): opaque dict supplied by the client
         """
 
         def _get_e2e_room_keys_version_info_txn(txn):
             if version is None:
                 this_version = self._get_current_version(txn, user_id)
             else:
-                this_version = version
+                try:
+                    this_version = int(version)
+                except ValueError:
+                    # Our versions are all ints so if we can't convert it to an integer,
+                    # it isn't there.
+                    raise StoreError(404, "No row found")
 
             result = self._simple_select_one_txn(
                 txn,
@@ -236,6 +250,7 @@ def _get_e2e_room_keys_version_info_txn(txn):
                 ),
             )
             result["auth_data"] = json.loads(result["auth_data"])
+            result["version"] = str(result["version"])
             return result
 
         return self.runInteraction(
diff --git a/synapse/storage/schema/delta/52/e2e_room_keys.sql b/synapse/storage/schema/delta/52/e2e_room_keys.sql
new file mode 100644
index 000000000000..db687cccae88
--- /dev/null
+++ b/synapse/storage/schema/delta/52/e2e_room_keys.sql
@@ -0,0 +1,53 @@
+/* Copyright 2018 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Change version column to an integer so we can do MAX() sensibly
+ */
+CREATE TABLE e2e_room_keys_versions_new (
+    user_id TEXT NOT NULL,
+    version BIGINT NOT NULL,
+    algorithm TEXT NOT NULL,
+    auth_data TEXT NOT NULL,
+    deleted SMALLINT DEFAULT 0 NOT NULL
+);
+
+INSERT INTO e2e_room_keys_versions_new
+    SELECT user_id, CAST(version as BIGINT), algorithm, auth_data, deleted FROM e2e_room_keys_versions;
+
+DROP TABLE e2e_room_keys_versions;
+ALTER TABLE e2e_room_keys_versions_new RENAME TO e2e_room_keys_versions;
+
+CREATE UNIQUE INDEX e2e_room_keys_versions_idx ON e2e_room_keys_versions(user_id, version);
+
+/* Change e2e_rooms_keys to match
+ */
+CREATE TABLE e2e_room_keys_new (
+    user_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    session_id TEXT NOT NULL,
+    version BIGINT NOT NULL,
+    first_message_index INT,
+    forwarded_count INT,
+    is_verified BOOLEAN,
+    session_data TEXT NOT NULL
+);
+
+INSERT INTO e2e_room_keys_new
+    SELECT user_id, room_id, session_id, CAST(version as BIGINT), first_message_index, forwarded_count, is_verified, session_data FROM e2e_room_keys;
+
+DROP TABLE e2e_room_keys;
+ALTER TABLE e2e_room_keys_new RENAME TO e2e_room_keys;
+
+CREATE UNIQUE INDEX e2e_room_keys_idx ON e2e_room_keys(user_id, room_id, session_id);