diff --git a/pgtype/int8_test.go b/pgtype/int8_test.go
new file mode 100644
index 00000000..c9401034
--- /dev/null
+++ b/pgtype/int8_test.go
@@ -0,0 +1,87 @@
+package pgtype_test
+
+import (
+	"bytes"
+	"math"
+	"testing"
+
+	"github.com/jackc/pgx"
+	"github.com/jackc/pgx/pgio"
+	"github.com/jackc/pgx/pgtype"
+)
+
+func TestInt8Transcode(t *testing.T) {
+	conn := mustConnectPgx(t)
+	defer mustClose(t, conn)
+
+	ps, err := conn.Prepare("test", "select $1::int8")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		result pgtype.Int8
+	}{
+		{result: pgtype.Int8(math.MinInt64)},
+		{result: pgtype.Int8(-1)},
+		{result: pgtype.Int8(0)},
+		{result: pgtype.Int8(1)},
+		{result: pgtype.Int8(math.MaxInt64)},
+	}
+
+	ps.FieldDescriptions[0].FormatCode = pgx.TextFormatCode
+	for i, tt := range tests {
+		inputBuf := &bytes.Buffer{}
+		err = tt.result.EncodeText(inputBuf)
+		if err != nil {
+			t.Errorf("TextFormat %d: %v", i, err)
+		}
+
+		var s string
+		err := conn.QueryRow("test", string(inputBuf.Bytes()[4:])).Scan(&s)
+		if err != nil {
+			t.Errorf("TextFormat %d: %v", i, err)
+		}
+
+		outputBuf := &bytes.Buffer{}
+		pgio.WriteInt32(outputBuf, int32(len(s)))
+		outputBuf.WriteString(s)
+		var r pgtype.Int8
+		err = r.DecodeText(outputBuf)
+		if err != nil {
+			t.Errorf("TextFormat %d: %v", i, err)
+		}
+
+		if r != tt.result {
+			t.Errorf("TextFormat %d: expected %v, got %v", i, tt.result, r)
+		}
+	}
+
+	ps.FieldDescriptions[0].FormatCode = pgx.BinaryFormatCode
+	for i, tt := range tests {
+		inputBuf := &bytes.Buffer{}
+		err = tt.result.EncodeBinary(inputBuf)
+		if err != nil {
+			t.Errorf("BinaryFormat %d: %v", i, err)
+		}
+
+		var buf []byte
+		err := conn.QueryRow("test", inputBuf.Bytes()[4:]).Scan(&buf)
+		if err != nil {
+			t.Errorf("BinaryFormat %d: %v", i, err)
+		}
+
+		outputBuf := &bytes.Buffer{}
+		pgio.WriteInt32(outputBuf, int32(len(buf)))
+		outputBuf.Write(buf)
+		var r pgtype.Int8
+		err = r.DecodeBinary(outputBuf)
+		if err != nil {
+			t.Errorf("BinaryFormat %d: %v", i, err)
+		}
+
+		if r != tt.result {
+			t.Errorf("BinaryFormat %d: expected %v, got %v", i, tt.result, r)
+		}
+	}
+}
diff --git a/pgtype/pgtype_test.go b/pgtype/pgtype_test.go
new file mode 100644
index 00000000..695fe688
--- /dev/null
+++ b/pgtype/pgtype_test.go
@@ -0,0 +1,31 @@
+package pgtype_test
+
+import (
+	"os"
+	"testing"
+
+	"github.com/jackc/pgx"
+)
+
+func mustConnectPgx(t testing.TB) *pgx.Conn {
+	config, err := pgx.ParseURI(os.Getenv("DATABASE_URL"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	conn, err := pgx.Connect(config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return conn
+}
+
+func mustClose(t testing.TB, conn interface {
+	Close() error
+}) {
+	err := conn.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}