diff --git a/.changeset/rich-fireants-happen.md b/.changeset/rich-fireants-happen.md
new file mode 100644
index 0000000000..9b51d05c4f
--- /dev/null
+++ b/.changeset/rich-fireants-happen.md
@@ -0,0 +1,5 @@
+---
+'@backstage/core-components': patch
+---
+
+Ensure that the "Custom User" sign-in makes use of supplied custom tokens, if any
diff --git a/packages/core-components/src/layout/SignInPage/customProvider.tsx b/packages/core-components/src/layout/SignInPage/customProvider.tsx
index 13ba906079..101c74d3cd 100644
--- a/packages/core-components/src/layout/SignInPage/customProvider.tsx
+++ b/packages/core-components/src/layout/SignInPage/customProvider.tsx
@@ -69,10 +69,11 @@ const Component: ProviderComponent = ({ onSignInSuccess }) => {
 
   const { errors } = formState;
 
-  const handleResult = ({ userId }: Data) => {
+  const handleResult = ({ userId, idToken }: Data) => {
     onSignInSuccess(
       UserIdentity.fromLegacy({
         userId,
+        getIdToken: idToken !== undefined ? async () => idToken : undefined,
         profile: {
           email: `${userId}@example.com`,
         },