diff --git a/pgtype/enum_codec.go b/pgtype/enum_codec.go
index 3bf29f4a..970895d8 100644
--- a/pgtype/enum_codec.go
+++ b/pgtype/enum_codec.go
@@ -76,10 +76,11 @@ func (c *EnumCodec) lookupAndCacheString(src []byte) string {
 
 	if s, found := c.membersMap[string(src)]; found {
 		return s
-	} else {
-		c.membersMap[s] = s
-		return s
 	}
+
+	s := string(src)
+	c.membersMap[s] = s
+	return s
 }
 
 type scanPlanTextAnyToEnumString struct {
diff --git a/pgtype/enum_codec_test.go b/pgtype/enum_codec_test.go
new file mode 100644
index 00000000..139bfc34
--- /dev/null
+++ b/pgtype/enum_codec_test.go
@@ -0,0 +1,69 @@
+package pgtype_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/jackc/pgx/v5/pgtype/testutil"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEnumCodec(t *testing.T) {
+	conn := testutil.MustConnectPgx(t)
+	defer testutil.MustCloseContext(t, conn)
+
+	_, err := conn.Exec(context.Background(), `drop type if exists enum_test;
+
+create type enum_test as enum ('foo', 'bar', 'baz');`)
+	require.NoError(t, err)
+	defer conn.Exec(context.Background(), "drop type enum_test")
+
+	dt, err := conn.LoadDataType(context.Background(), "enum_test")
+	require.NoError(t, err)
+
+	conn.ConnInfo().RegisterDataType(*dt)
+
+	var s string
+	err = conn.QueryRow(context.Background(), `select 'foo'::enum_test`).Scan(&s)
+	require.NoError(t, err)
+	require.Equal(t, "foo", s)
+
+	err = conn.QueryRow(context.Background(), `select $1::enum_test`, "bar").Scan(&s)
+	require.NoError(t, err)
+	require.Equal(t, "bar", s)
+
+	err = conn.QueryRow(context.Background(), `select 'foo'::enum_test`).Scan(&s)
+	require.NoError(t, err)
+	require.Equal(t, "foo", s)
+
+	err = conn.QueryRow(context.Background(), `select $1::enum_test`, "bar").Scan(&s)
+	require.NoError(t, err)
+	require.Equal(t, "bar", s)
+
+	err = conn.QueryRow(context.Background(), `select 'baz'::enum_test`).Scan(&s)
+	require.NoError(t, err)
+	require.Equal(t, "baz", s)
+}
+
+func TestEnumCodecValues(t *testing.T) {
+	conn := testutil.MustConnectPgx(t)
+	defer testutil.MustCloseContext(t, conn)
+
+	_, err := conn.Exec(context.Background(), `drop type if exists enum_test;
+
+create type enum_test as enum ('foo', 'bar', 'baz');`)
+	require.NoError(t, err)
+	defer conn.Exec(context.Background(), "drop type enum_test")
+
+	dt, err := conn.LoadDataType(context.Background(), "enum_test")
+	require.NoError(t, err)
+
+	conn.ConnInfo().RegisterDataType(*dt)
+
+	rows, err := conn.Query(context.Background(), `select 'foo'::enum_test`)
+	require.NoError(t, err)
+	require.True(t, rows.Next())
+	values, err := rows.Values()
+	require.NoError(t, err)
+	require.Equal(t, values, []interface{}{"foo"})
+}