diff --git a/value_reader.go b/value_reader.go
index 6e552ea8..a4897543 100644
--- a/value_reader.go
+++ b/value_reader.go
@@ -60,6 +60,20 @@ func (r *ValueReader) ReadInt16() int16 {
 	return r.mr.readInt16()
 }
 
+func (r *ValueReader) ReadUint16() uint16 {
+	if r.err != nil {
+		return 0
+	}
+
+	r.valueBytesRemaining -= 2
+	if r.valueBytesRemaining < 0 {
+		r.Fatal(errors.New("read past end of value"))
+		return 0
+	}
+
+	return r.mr.readUint16()
+}
+
 func (r *ValueReader) ReadInt32() int32 {
 	if r.err != nil {
 		return 0
diff --git a/values.go b/values.go
index 69fdaae0..ae7b7cf7 100644
--- a/values.go
+++ b/values.go
@@ -453,7 +453,7 @@ func (n NullCid) Encode(w *WriteBuf, oid Oid) error {
 // Its conversion functions can be found in src/backend/utils/adt/tid.c
 // in the PostgreSQL sources.
 type Tid struct {
-	BlockNumber  uint16
+	BlockNumber  uint32
 	OffsetNumber uint16
 }
 
@@ -473,7 +473,7 @@ func (n *NullTid) Scan(vr *ValueReader) error {
 	}
 
 	if vr.Len() == -1 {
-		n.Tid, n.Valid = 0, false
+		n.Tid, n.Valid = Tid{BlockNumber: 0, OffsetNumber: 0}, false
 		return nil
 	}
 	n.Valid = true
@@ -1639,13 +1639,13 @@ func decodeTid(vr *ValueReader) Tid {
 		if err != nil {
 			vr.Fatal(ProtocolError(fmt.Sprintf("Received invalid offsetNumber part of a Tid: %v", s)))
 		}
-		return Tid{BlockNumber: blockNumber, OffsetNumber: offsetNumber}
+		return Tid{BlockNumber: uint32(blockNumber), OffsetNumber: uint16(offsetNumber)}
 	case BinaryFormatCode:
-		if vr.Len() != 4 {
+		if vr.Len() != 6 {
 			vr.Fatal(ProtocolError(fmt.Sprintf("Received an invalid size for an Oid: %d", vr.Len())))
 			return Tid{BlockNumber: 0, OffsetNumber: 0}
 		}
-		return Tid{BlockNumber: vr.ReadUint16(), OffsetNumber: vr.ReadUint16()}
+		return Tid{BlockNumber: vr.ReadUint32(), OffsetNumber: vr.ReadUint16()}
 	default:
 		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
 		return Tid{BlockNumber: 0, OffsetNumber: 0}
@@ -1657,9 +1657,9 @@ func encodeTid(w *WriteBuf, oid Oid, value Tid) error {
 		return fmt.Errorf("cannot encode Go %s into oid %d", "pgx.Tid", oid)
 	}
 
-	w.WriteInt32(4)
-	w.WriteUint16(uint16(value.BlockNumber))
-	w.WriteUint16(uint16(value.OffsetNumber))
+	w.WriteInt32(6)
+	w.WriteUint32(value.BlockNumber)
+	w.WriteUint16(value.OffsetNumber)
 
 	return nil
 }
diff --git a/values_test.go b/values_test.go
index 2325b6f1..cea70b9c 100644
--- a/values_test.go
+++ b/values_test.go
@@ -596,6 +596,7 @@ func TestNullX(t *testing.T) {
 		i32 pgx.NullInt32
 		xid pgx.NullXid
 		cid pgx.NullCid
+		tid pgx.NullTid
 		i64 pgx.NullInt64
 		f32 pgx.NullFloat32
 		f64 pgx.NullFloat64
@@ -623,6 +624,9 @@ func TestNullX(t *testing.T) {
 		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 1, Valid: true}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 1, Valid: true}}},
 		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 1, Valid: false}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 0, Valid: false}}},
 		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 4294967295, Valid: true}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 4294967295, Valid: true}}},
+		{"select $1::tid", []interface{}{pgx.NullTid{Tid: pgx.Tid{BlockNumber: 1, OffsetNumber: 1}, Valid: true}}, []interface{}{&actual.tid}, allTypes{tid: pgx.NullTid{Tid: pgx.Tid{BlockNumber: 1, OffsetNumber: 1}, Valid: true}}},
+		{"select $1::tid", []interface{}{pgx.NullTid{Tid: pgx.Tid{BlockNumber: 1, OffsetNumber: 1}, Valid: false}}, []interface{}{&actual.tid}, allTypes{tid: pgx.NullTid{Tid: pgx.Tid{BlockNumber: 0, OffsetNumber: 0}, Valid: false}}},
+		{"select $1::tid", []interface{}{pgx.NullTid{Tid: pgx.Tid{BlockNumber: 4294967295, OffsetNumber: 65535}, Valid: true}}, []interface{}{&actual.tid}, allTypes{tid: pgx.NullTid{Tid: pgx.Tid{BlockNumber: 4294967295, OffsetNumber: 65535}, Valid: true}}},
 		{"select $1::int8", []interface{}{pgx.NullInt64{Int64: 1, Valid: true}}, []interface{}{&actual.i64}, allTypes{i64: pgx.NullInt64{Int64: 1, Valid: true}}},
 		{"select $1::int8", []interface{}{pgx.NullInt64{Int64: 1, Valid: false}}, []interface{}{&actual.i64}, allTypes{i64: pgx.NullInt64{Int64: 0, Valid: false}}},
 		{"select $1::float4", []interface{}{pgx.NullFloat32{Float32: 1.23, Valid: true}}, []interface{}{&actual.f32}, allTypes{f32: pgx.NullFloat32{Float32: 1.23, Valid: true}}},