diff --git a/backend/src/server/routes/v2/project-membership-router.ts b/backend/src/server/routes/v2/project-membership-router.ts
index 4aa03f33c..0c3ceb01e 100644
--- a/backend/src/server/routes/v2/project-membership-router.ts
+++ b/backend/src/server/routes/v2/project-membership-router.ts
@@ -27,7 +27,7 @@ export const registerProjectMembershipRouter = async (server: FastifyZodProvider
       body: z.object({
         emails: z.string().email().array().default([]).describe(PROJECT_USERS.INVITE_MEMBER.emails),
         usernames: z.string().array().default([]).describe(PROJECT_USERS.INVITE_MEMBER.usernames),
-        roleSlugs: z.string().array().optional().describe(PROJECT_USERS.INVITE_MEMBER.roleSlugs)
+        roleSlugs: z.string().array().min(1).optional().describe(PROJECT_USERS.INVITE_MEMBER.roleSlugs)
       }),
       response: {
         200: z.object({
@@ -49,7 +49,7 @@ export const registerProjectMembershipRouter = async (server: FastifyZodProvider
         projects: [
           {
             id: req.params.projectId,
-            projectRoleSlug: [ProjectMembershipRole.Member]
+            projectRoleSlug: req.body.roleSlugs || [ProjectMembershipRole.Member]
           }
         ]
       });