diff --git a/oioioi/problems/migrations/0039_alter_algorithmtagproposal_unique_together_and_more.py b/oioioi/problems/migrations/0039_alter_algorithmtagproposal_unique_together_and_more.py
new file mode 100644
index 000000000..1a0478c8d
--- /dev/null
+++ b/oioioi/problems/migrations/0039_alter_algorithmtagproposal_unique_together_and_more.py
@@ -0,0 +1,64 @@
+# Generated by Django 5.2.7 on 2025-11-17 22:44
+
+from django.conf import settings
+from django.db import migrations
+from django.db.models import Count
+
+def cleanup_duplicate_proposals(apps, schema_editor):
+    AlgorithmTagProposal = apps.get_model('problems', 'AlgorithmTagProposal')
+    DifficultyTagProposal = apps.get_model('problems', 'DifficultyTagProposal')
+
+    # Cleanup AlgorithmTagProposal
+    duplicates = (
+        AlgorithmTagProposal.objects.values('problem', 'tag', 'user')
+        .annotate(count=Count('id'))
+        .filter(count__gt=1)
+    )
+
+    for duplicate in duplicates:
+        proposals = AlgorithmTagProposal.objects.filter(
+            problem=duplicate['problem'],
+            tag=duplicate['tag'],
+            user=duplicate['user']
+        ).order_by('id')
+        
+        # Keep the first one, delete the rest
+        for proposal in proposals[1:]:
+            proposal.delete()
+
+    # Cleanup DifficultyTagProposal
+    duplicates = (
+        DifficultyTagProposal.objects.values('problem', 'user')
+        .annotate(count=Count('id'))
+        .filter(count__gt=1)
+    )
+
+    for duplicate in duplicates:
+        proposals = DifficultyTagProposal.objects.filter(
+            problem=duplicate['problem'],
+            user=duplicate['user']
+        ).order_by('id')
+
+        # Keep the first one, delete the rest
+        for proposal in proposals[1:]:
+            proposal.delete()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('problems', '0038_alter_algorithmtaglocalization_language_and_more'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.RunPython(cleanup_duplicate_proposals),
+        migrations.AlterUniqueTogether(
+            name='algorithmtagproposal',
+            unique_together={('problem', 'tag', 'user')},
+        ),
+        migrations.AlterUniqueTogether(
+            name='difficultytagproposal',
+            unique_together={('problem', 'user')},
+        ),
+    ]
diff --git a/oioioi/problems/models.py b/oioioi/problems/models.py
index e38c740fe..e78511f90 100644
--- a/oioioi/problems/models.py
+++ b/oioioi/problems/models.py
@@ -797,6 +797,7 @@ def __str__(self):
         return str(self.problem.name) + " -- " + str(self.tag.name)
 
     class Meta:
+        unique_together = ("problem", "user")
         verbose_name = _("difficulty proposal")
         verbose_name_plural = _("difficulty proposals")
 
@@ -878,6 +879,7 @@ def __str__(self):
         return str(self.problem.name) + " -- " + str(self.tag.name)
 
     class Meta:
+        unique_together = ("problem", "tag", "user")
         verbose_name = _("algorithm tag proposal")
         verbose_name_plural = _("algorithm tag proposals")