diff --git a/upstream/upstream_dot_test.go b/upstream/upstream_dot_test.go
index ca93bb0ff..0b14f6f2e 100644
--- a/upstream/upstream_dot_test.go
+++ b/upstream/upstream_dot_test.go
@@ -76,6 +76,8 @@ func TestUpstream_dnsOverTLS_race(t *testing.T) {
 	wg.Wait()
 }
 
+// TODO(e.burkov, a.garipov):  Add to golibs and use here some kind of helper
+// for type assertion of interface types.
 func TestUpstream_dnsOverTLS_poolReconnect(t *testing.T) {
 	srv := startDoTServer(t, func(w dns.ResponseWriter, req *dns.Msg) {
 		resp := respondToTestMessage(req)
@@ -119,7 +121,8 @@ func TestUpstream_dnsOverTLS_poolReconnect(t *testing.T) {
 
 	// Now let's close the pooled connection.
 	conn := p.conns.Get()
-	usedConn = testutil.RequireTypeAssert[net.Conn](t, conn)
+	require.Implements(t, (*net.Conn)(nil), conn)
+	usedConn, _ = conn.(net.Conn)
 
 	require.NoError(t, usedConn.Close())
 
@@ -134,7 +137,7 @@ func TestUpstream_dnsOverTLS_poolReconnect(t *testing.T) {
 
 	// Now assert that the number of connections in the pool is not changed.
 	conn = p.conns.Get()
-	_ = testutil.RequireTypeAssert[net.Conn](t, conn)
+	require.Implements(t, (*net.Conn)(nil), conn)
 
 	require.Nil(t, p.conns.Get())
 	assert.NotSame(t, usedConn, conn)
@@ -174,7 +177,8 @@ func TestUpstream_dnsOverTLS_poolDeadline(t *testing.T) {
 
 	// Now let's get connection from the pool and use it again.
 	conn := p.conns.Get()
-	usedConn := testutil.RequireTypeAssert[net.Conn](t, conn)
+	require.Implements(t, (*net.Conn)(nil), conn)
+	usedConn := conn.(net.Conn)
 
 	response, err = p.exchangeWithConn(usedConn, req)
 	require.NoError(t, err)
diff --git a/upstream/upstream_dot_windows.go b/upstream/upstream_dot_windows.go
index a2349adcf..003b2ec38 100644
--- a/upstream/upstream_dot_windows.go
+++ b/upstream/upstream_dot_windows.go
@@ -7,7 +7,7 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-// isConnBroken always returns false.
+// isConnBroken returns true if err means that a connection is broken.
 func isConnBroken(err error) (ok bool) {
 	return errors.Is(err, windows.WSAECONNABORTED)
 }