diff --git a/backend/internal/data/repo/repo_item_attachments.go b/backend/internal/data/repo/repo_item_attachments.go
index 7be4d7fe..d4f8e568 100644
--- a/backend/internal/data/repo/repo_item_attachments.go
+++ b/backend/internal/data/repo/repo_item_attachments.go
@@ -87,11 +87,11 @@ func (r *AttachmentRepo) Get(ctx context.Context, id uuid.UUID) (*ent.Attachment
 		Only(ctx)
 }
 
-func (r *AttachmentRepo) Update(ctx context.Context, itemID uuid.UUID, data *ItemAttachmentUpdate) (*ent.Attachment, error) {
+func (r *AttachmentRepo) Update(ctx context.Context, id uuid.UUID, data *ItemAttachmentUpdate) (*ent.Attachment, error) {
 	// TODO: execute within Tx
 	typ := attachment.Type(data.Type)
 
-	bldr := r.db.Attachment.UpdateOneID(itemID).
+	bldr := r.db.Attachment.UpdateOneID(id).
 		SetType(typ)
 
 	// Primary only applies to photos
@@ -101,7 +101,12 @@ func (r *AttachmentRepo) Update(ctx context.Context, itemID uuid.UUID, data *Ite
 		bldr = bldr.SetPrimary(false)
 	}
 
-	itm, err := bldr.Save(ctx)
+	updatedAttachment, err := bldr.Save(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	attachmentItem, err := updatedAttachment.QueryItem().Only(ctx)
 	if err != nil {
 		return nil, err
 	}
@@ -109,8 +114,8 @@ func (r *AttachmentRepo) Update(ctx context.Context, itemID uuid.UUID, data *Ite
 	// Ensure all other attachments are not primary
 	err = r.db.Attachment.Update().
 		Where(
-			attachment.HasItemWith(item.ID(itemID)),
-			attachment.IDNEQ(itm.ID),
+			attachment.HasItemWith(item.ID(attachmentItem.ID)),
+			attachment.IDNEQ(updatedAttachment.ID),
 		).
 		SetPrimary(false).
 		Exec(ctx)
@@ -118,7 +123,7 @@ func (r *AttachmentRepo) Update(ctx context.Context, itemID uuid.UUID, data *Ite
 		return nil, err
 	}
 
-	return r.Get(ctx, itm.ID)
+	return r.Get(ctx, updatedAttachment.ID)
 }
 
 func (r *AttachmentRepo) Delete(ctx context.Context, id uuid.UUID) error {
diff --git a/backend/internal/data/repo/repo_item_attachments_test.go b/backend/internal/data/repo/repo_item_attachments_test.go
index 22a2256c..1dd922b9 100644
--- a/backend/internal/data/repo/repo_item_attachments_test.go
+++ b/backend/internal/data/repo/repo_item_attachments_test.go
@@ -133,3 +133,25 @@ func TestAttachmentRepo_Delete(t *testing.T) {
 	_, err = tRepos.Attachments.Get(context.Background(), entity.ID)
 	require.Error(t, err)
 }
+
+func TestAttachmentRepo_EnsureSinglePrimaryAttachment(t *testing.T) {
+	ctx := context.Background()
+	attachments := useAttachments(t, 2)
+
+	setAndVerifyPrimary := func(primaryAttachmentID, nonPrimaryAttachmentID uuid.UUID) {
+		primaryAttachment, err := tRepos.Attachments.Update(ctx, primaryAttachmentID, &ItemAttachmentUpdate{
+			Type:    attachment.TypePhoto.String(),
+			Primary: true,
+		})
+		require.NoError(t, err)
+
+		nonPrimaryAttachment, err := tRepos.Attachments.Get(ctx, nonPrimaryAttachmentID)
+		require.NoError(t, err)
+
+		assert.True(t, primaryAttachment.Primary)
+		assert.False(t, nonPrimaryAttachment.Primary)
+	}
+
+	setAndVerifyPrimary(attachments[0].ID, attachments[1].ID)
+	setAndVerifyPrimary(attachments[1].ID, attachments[0].ID)
+}