diff --git a/app/assets/javascripts/vue_shared/components/user_select/user_select.vue b/app/assets/javascripts/vue_shared/components/user_select/user_select.vue
index 94166d74c1abf6bdf445960af8df17cd5ea7b1d4..028e19a6f9478ad4e70aeb1cf9f4bb1bb6eed885 100644
--- a/app/assets/javascripts/vue_shared/components/user_select/user_select.vue
+++ b/app/assets/javascripts/vue_shared/components/user_select/user_select.vue
@@ -113,7 +113,9 @@ export default {
       update(data) {
         // TODO Remove null filter (BE fix required)
         // https://gitlab.com/gitlab-org/gitlab/-/issues/329750
-        return data.workspace?.users?.nodes.filter((x) => x).map(({ user }) => user) || [];
+        const users = data.workspace?.users?.nodes.filter((x) => x).map(({ user }) => user) || [];
+        // User field is nullable and we only want to display non-null users
+        return users.filter((u) => u);
       },
       debounce: ASSIGNEES_DEBOUNCE_DELAY,
       error({ graphQLErrors }) {
diff --git a/ee/app/assets/javascripts/boards/stores/actions.js b/ee/app/assets/javascripts/boards/stores/actions.js
index a18a31f258452b94f712c9def26f2f37748974b3..cd2de986cbad4657b1db994f95547775c30b88cf 100644
--- a/ee/app/assets/javascripts/boards/stores/actions.js
+++ b/ee/app/assets/javascripts/boards/stores/actions.js
@@ -535,14 +535,15 @@ export default {
       })
       .then(({ data }) => {
         const [firstError] = data.workspace.errors || [];
-        const assignees = data.workspace.assignees.nodes;
+        const assignees = data.workspace.assignees.nodes.map(({ user }) => user);
 
         if (firstError) {
           throw new Error(firstError);
         }
         commit(
           types.RECEIVE_ASSIGNEES_SUCCESS,
-          assignees.map(({ user }) => user),
+          // User field is nullable and we only want to display non-null users
+          assignees.filter((u) => u),
         );
       })
       .catch((e) => {