diff --git a/keyserver/src/responders/thread-responders.js b/keyserver/src/responders/thread-responders.js
--- a/keyserver/src/responders/thread-responders.js
+++ b/keyserver/src/responders/thread-responders.js
@@ -43,7 +43,7 @@
 
 const threadDeletionRequestInputValidator = tShape({
   threadID: t.String,
-  accountPassword: tPassword,
+  accountPassword: t.maybe(tPassword),
 });
 
 async function threadDeletionResponder(
diff --git a/lib/actions/thread-actions.js b/lib/actions/thread-actions.js
--- a/lib/actions/thread-actions.js
+++ b/lib/actions/thread-actions.js
@@ -23,7 +23,7 @@
   callServerEndpoint: CallServerEndpoint,
 ): ((
   threadID: string,
-  currentAccountPassword: string,
+  currentAccountPassword: ?string,
 ) => Promise<LeaveThreadPayload>) => async (
   threadID,
   currentAccountPassword,
diff --git a/lib/types/thread-types.js b/lib/types/thread-types.js
--- a/lib/types/thread-types.js
+++ b/lib/types/thread-types.js
@@ -299,7 +299,7 @@
 
 export type ThreadDeletionRequest = {
   +threadID: string,
-  +accountPassword: string,
+  +accountPassword: ?string,
 };
 
 export type RemoveMembersRequest = {