diff --git a/src/crypto/EncryptionSetup.ts b/src/crypto/EncryptionSetup.ts
index b8f52fcdc..2c8384467 100644
--- a/src/crypto/EncryptionSetup.ts
+++ b/src/crypto/EncryptionSetup.ts
@@ -188,7 +188,7 @@ export class EncryptionSetupOperation {
             // We must only call `uploadDeviceSigningKeys` from inside this auth
             // helper to ensure we properly handle auth errors.
             await this.crossSigningKeys.authUpload?.((authDict) => {
-                return baseApis.uploadDeviceSigningKeys(authDict, keys as CrossSigningKeys);
+                return baseApis.uploadDeviceSigningKeys(authDict ?? undefined, keys as CrossSigningKeys);
             });
 
             // pass the new keys to the main instance of our own CrossSigningInfo.
diff --git a/src/interactive-auth.ts b/src/interactive-auth.ts
index e85ac9c27..0a75ab523 100644
--- a/src/interactive-auth.ts
+++ b/src/interactive-auth.ts
@@ -159,11 +159,12 @@ export class NoAuthFlowFoundError extends Error {
  * The type of an application callback to perform the user-interactive bit of UIA.
  *
  * It is called with a single parameter, `makeRequest`, which is a function which takes the UIA parameters and
- * makes the HTTP request.
+ * makes the HTTP request. The `authData` parameter in `makeRequest` can be set to null to omit the `auth` field
+ * from the UIA request.
  *
  * The generic parameter `T` is the type of the response of the endpoint, once it is eventually successful.
  */
-export type UIAuthCallback<T> = (makeRequest: (authData: IAuthDict) => Promise<UIAResponse<T>>) => Promise<T>;
+export type UIAuthCallback<T> = (makeRequest: (authData: IAuthDict | null) => Promise<UIAResponse<T>>) => Promise<T>;
 
 interface IOpts<T> {
     /**
diff --git a/src/rust-crypto/OutgoingRequestProcessor.ts b/src/rust-crypto/OutgoingRequestProcessor.ts
index 20c0b93fa..213f8dd84 100644
--- a/src/rust-crypto/OutgoingRequestProcessor.ts
+++ b/src/rust-crypto/OutgoingRequestProcessor.ts
@@ -116,11 +116,13 @@ export class OutgoingRequestProcessor {
         }
 
         const parsedBody = JSON.parse(body);
-        const makeRequest = async (auth: IAuthDict): Promise<UIAResponse<T>> => {
-            const newBody = {
+        const makeRequest = async (auth: IAuthDict | null): Promise<UIAResponse<T>> => {
+            const newBody: Record<string, any> = {
                 ...parsedBody,
-                auth,
             };
+            if (auth !== null) {
+                newBody.auth = auth;
+            }
             const resp = await this.rawJsonRequest(method, path, queryParams, JSON.stringify(newBody));
             return JSON.parse(resp) as T;
         };