diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -1051,8 +1051,12 @@
   return !!memberInfo.permissions[threadPermissions.CHANGE_ROLE]?.value;
 }
 
+function roleIsDefaultRole(roleInfo: ?RoleInfo): boolean {
+  return !!(roleInfo && roleInfo.specialRole === specialRoles.DEFAULT_ROLE);
+}
+
 function roleIsAdminRole(roleInfo: ?RoleInfo): boolean {
-  return !!(roleInfo && !roleInfo.isDefault && roleInfo.name === 'Admins');
+  return !!(roleInfo && roleInfo.specialRole === specialRoles.ADMIN_ROLE);
 }
 
 function threadHasAdminRole(
@@ -1370,8 +1374,8 @@
 }
 
 function checkIfDefaultMembersAreVoiced(threadInfo: ThreadInfo): boolean {
-  const defaultRoleID = Object.keys(threadInfo.roles).find(
-    roleID => threadInfo.roles[roleID].isDefault,
+  const defaultRoleID = Object.keys(threadInfo.roles).find(roleID =>
+    roleIsDefaultRole(threadInfo.roles[roleID]),
   );
   invariant(
     defaultRoleID !== undefined,
@@ -1560,7 +1564,7 @@
   if (
     canRemoveMembers &&
     !memberInfo.isViewer &&
-    (canChangeRoles || threadInfo.roles[role]?.isDefault)
+    (canChangeRoles || roleIsDefaultRole(threadInfo.roles[role]))
   ) {
     result.push('remove_user');
   }
@@ -1792,6 +1796,7 @@
   threadTypeDescriptions,
   memberIsAdmin,
   memberHasAdminPowers,
+  roleIsDefaultRole,
   roleIsAdminRole,
   threadHasAdminRole,
   identifyInvalidatedThreads,