diff --git a/internal/db/bundb/errors.go b/internal/db/bundb/errors.go
index 46735ca80..c8f39aebd 100644
--- a/internal/db/bundb/errors.go
+++ b/internal/db/bundb/errors.go
@@ -20,7 +20,7 @@ package bundb
 import (
 	"errors"
 
-	"github.com/jackc/pgconn"
+	"github.com/jackc/pgx/v5/pgconn"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"modernc.org/sqlite"
 	sqlite3 "modernc.org/sqlite/lib"
diff --git a/internal/db/bundb/errors_test.go b/internal/db/bundb/errors_test.go
new file mode 100644
index 000000000..400780196
--- /dev/null
+++ b/internal/db/bundb/errors_test.go
@@ -0,0 +1,114 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package bundb_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+)
+
+type ErrorsTestSuite struct {
+	BunDBStandardTestSuite
+}
+
+func (suite *ErrorsTestSuite) TestErrorAlreadyExists() {
+	type testType struct {
+		follow   *gtsmodel.Follow
+		expected error
+	}
+
+	var (
+		ctx           = context.Background()
+		initialFollow = &gtsmodel.Follow{
+			ID:              "01HD11D8JH5V64GJRFDA7VFNDX",
+			URI:             "https://example.org/unique_uri",
+			AccountID:       "01HD11E9Y02HVXZ4YB20SG4QR9",
+			TargetAccountID: "01HD11EPJWM919DRP9JCKDZBX6",
+		}
+		editFollow = func(f func(*gtsmodel.Follow)) *gtsmodel.Follow {
+			edited := new(gtsmodel.Follow)
+			*edited = *initialFollow
+
+			f(edited)
+			return edited
+		}
+	)
+
+	// Put the initial follow so we have
+	// a constraint in place to fail on.
+	if err := suite.db.PutFollow(ctx, initialFollow); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	for i, test := range []testType{
+		{
+			// Try to put the initial follow in again.
+			follow:   initialFollow,
+			expected: db.ErrAlreadyExists,
+		},
+		{
+			// Different ID but same URI,
+			// should fail on URI constraint.
+			follow: editFollow(func(f *gtsmodel.Follow) {
+				f.ID = "01HD12ASEEBZ7MRY8AK51RJ20Y"
+			}),
+			expected: db.ErrAlreadyExists,
+		},
+		{
+			// Different URI but same ID,
+			// should fail on ID constraint.
+			follow: editFollow(func(f *gtsmodel.Follow) {
+				f.URI = "https://example.org/new_uri"
+			}),
+			expected: db.ErrAlreadyExists,
+		},
+		{
+			// Different ID and URI, but same account and
+			// target. Should fail on unique constraint.
+			follow: editFollow(func(f *gtsmodel.Follow) {
+				f.ID = "01HD12ASEEBZ7MRY8AK51RJ20Y"
+				f.URI = "https://example.org/new_uri"
+			}),
+			expected: db.ErrAlreadyExists,
+		},
+		{
+			// Put a follow with different ID, URI,
+			// and AccountID. This should work fine.
+			follow: editFollow(func(f *gtsmodel.Follow) {
+				f.ID = "01HD12ASEEBZ7MRY8AK51RJ20Y"
+				f.URI = "https://example.org/new_uri"
+				f.AccountID = "01HD12DTPDR8A96S5K5M7SJAF3"
+			}),
+			expected: nil,
+		},
+	} {
+		err := suite.db.PutFollow(ctx, test.follow)
+		if !errors.Is(err, test.expected) {
+			suite.Fail("", "test number %d expected %v, got %v", i+1, test.expected, err)
+		}
+	}
+}
+
+func TestErrorsTestSuite(t *testing.T) {
+	suite.Run(t, new(ErrorsTestSuite))
+}