diff --git a/backend/src/services/identity-project/identity-project-service.ts b/backend/src/services/identity-project/identity-project-service.ts
index 10274f001..7f9cf920e 100644
--- a/backend/src/services/identity-project/identity-project-service.ts
+++ b/backend/src/services/identity-project/identity-project-service.ts
@@ -185,7 +185,7 @@ export const identityProjectServiceFactory = ({
       ({ role }) =>
         !Object.values(ProjectMembershipRole)
           // we don't want to include custom in this check;
-          // this unintentionally lets users set slug to custom which is reserved
+          // this unintentionally enables setting slug to custom which is reserved
           .filter((r) => r !== ProjectMembershipRole.Custom)
           .includes(role as ProjectMembershipRole)
     );
diff --git a/backend/src/services/project-membership/project-membership-service.ts b/backend/src/services/project-membership/project-membership-service.ts
index 74b830c6d..b4826b54b 100644
--- a/backend/src/services/project-membership/project-membership-service.ts
+++ b/backend/src/services/project-membership/project-membership-service.ts
@@ -280,7 +280,12 @@ export const projectMembershipServiceFactory = ({
 
     // validate custom roles input
     const customInputRoles = roles.filter(
-      ({ role }) => !Object.values(ProjectMembershipRole).includes(role as ProjectMembershipRole)
+      ({ role }) =>
+        !Object.values(ProjectMembershipRole)
+          // we don't want to include custom in this check;
+          // this unintentionally enables setting slug to custom which is reserved
+          .filter((r) => r !== ProjectMembershipRole.Custom)
+          .includes(role as ProjectMembershipRole)
     );
     const hasCustomRole = Boolean(customInputRoles.length);
     if (hasCustomRole) {