diff --git a/changelog.d/6189.misc b/changelog.d/6189.misc
new file mode 100644
index 0000000000..a66eb384e6
--- /dev/null
+++ b/changelog.d/6189.misc
@@ -0,0 +1 @@
+Make `version` optional in body of `PUT /room_keys/version/{version}`, since it's redundant.
diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py
index a9d80f708c..0cea445f0d 100644
--- a/synapse/handlers/e2e_room_keys.py
+++ b/synapse/handlers/e2e_room_keys.py
@@ -352,8 +352,8 @@ class E2eRoomKeysHandler(object):
             A deferred of an empty dict.
         """
         if "version" not in version_info:
-            raise SynapseError(400, "Missing version in body", Codes.MISSING_PARAM)
-        if version_info["version"] != version:
+            version_info["version"] = version
+        elif version_info["version"] != version:
             raise SynapseError(
                 400, "Version in body does not match", Codes.INVALID_PARAM
             )
diff --git a/synapse/rest/client/v2_alpha/room_keys.py b/synapse/rest/client/v2_alpha/room_keys.py
index df4f44cd36..d596786430 100644
--- a/synapse/rest/client/v2_alpha/room_keys.py
+++ b/synapse/rest/client/v2_alpha/room_keys.py
@@ -375,7 +375,7 @@ class RoomKeysVersionServlet(RestServlet):
                     "ed25519:something": "hijklmnop"
                 }
             },
-            "version": "42"
+            "version": "12345"
         }
 
         HTTP/1.1 200 OK
diff --git a/tests/handlers/test_e2e_room_keys.py b/tests/handlers/test_e2e_room_keys.py
index c4503c1611..0bb96674a2 100644
--- a/tests/handlers/test_e2e_room_keys.py
+++ b/tests/handlers/test_e2e_room_keys.py
@@ -187,9 +187,8 @@ class E2eRoomKeysHandlerTestCase(unittest.TestCase):
         self.assertEqual(res, 404)
 
     @defer.inlineCallbacks
-    def test_update_bad_version(self):
-        """Check that we get a 400 if the version in the body is missing or
-        doesn't match
+    def test_update_omitted_version(self):
+        """Check that the update succeeds if the version is missing from the body
         """
         version = yield self.handler.create_version(
             self.local_user,
@@ -197,19 +196,35 @@ class E2eRoomKeysHandlerTestCase(unittest.TestCase):
         )
         self.assertEqual(version, "1")
 
-        res = None
-        try:
-            yield self.handler.update_version(
-                self.local_user,
-                version,
-                {
-                    "algorithm": "m.megolm_backup.v1",
-                    "auth_data": "revised_first_version_auth_data",
-                },
-            )
-        except errors.SynapseError as e:
-            res = e.code
-        self.assertEqual(res, 400)
+        yield self.handler.update_version(
+            self.local_user,
+            version,
+            {
+                "algorithm": "m.megolm_backup.v1",
+                "auth_data": "revised_first_version_auth_data",
+            },
+        )
+
+        # check we can retrieve it as the current version
+        res = yield self.handler.get_version_info(self.local_user)
+        self.assertDictEqual(
+            res,
+            {
+                "algorithm": "m.megolm_backup.v1",
+                "auth_data": "revised_first_version_auth_data",
+                "version": version,
+            },
+        )
+
+    @defer.inlineCallbacks
+    def test_update_bad_version(self):
+        """Check that we get a 400 if the version in the body doesn't match
+        """
+        version = yield self.handler.create_version(
+            self.local_user,
+            {"algorithm": "m.megolm_backup.v1", "auth_data": "first_version_auth_data"},
+        )
+        self.assertEqual(version, "1")
 
         res = None
         try: