diff --git a/lib/services/collection_service.dart b/lib/services/collection_service.dart
index 523c4cb..4e3d261 100644
--- a/lib/services/collection_service.dart
+++ b/lib/services/collection_service.dart
@@ -374,24 +374,22 @@ class CollectionService {
       throw Exception('Collection owner cannot be removed.');
     }
 
-    final targetMembership = await supabase
-        .from('collection_members')
-        .select('id, role')
-        .eq('collection_id', collectionId)
-        .eq('user_id', memberUserId)
-        .maybeSingle();
+    final members = await getMembers(collectionId);
+    final targetMembership = members.where((member) => member.userId == memberUserId);
 
-    if (targetMembership == null) {
+    if (targetMembership.isEmpty) {
       throw Exception('Member not found in this collection.');
     }
-    if (targetMembership['role'] == 'owner') {
+    final target = targetMembership.first;
+    if (target.role == 'owner') {
       throw Exception('Collection owner cannot be removed.');
     }
 
     final deleted = await supabase
         .from('collection_members')
         .delete()
-        .eq('id', targetMembership['id'] as String)
+      .eq('collection_id', collectionId)
+      .eq('user_id', memberUserId)
         .select('id');
 
     if (deleted.isEmpty) {