diff --git a/frontend/src/lib/gql/gql-client.ts b/frontend/src/lib/gql/gql-client.ts
index 1ac423236..124743f60 100644
--- a/frontend/src/lib/gql/gql-client.ts
+++ b/frontend/src/lib/gql/gql-client.ts
@@ -62,7 +62,9 @@ function createGqlClient(_gqlEndpoint?: string): Client {
               cache.invalidate({__typename: 'User', id: args.input.userId});
             },
             bulkAddProjectMembers: (result, args: BulkAddProjectMembersMutationVariables, cache, _info) => {
-              cache.invalidate({__typename: 'Project', id: args.input.projectId});
+              if (args.input.projectId) {
+                cache.invalidate({__typename: 'Project', id: args.input.projectId});
+              }
             },
             leaveProject: (result, args: LeaveProjectMutationVariables, cache, _info) => {
               cache.invalidate({__typename: 'Project', id: args.input.projectId});