diff --git a/conn.go b/conn.go
index b5f0dc5d..e41d4869 100644
--- a/conn.go
+++ b/conn.go
@@ -455,7 +455,7 @@ func (c *Conn) sendPreparedQuery(ps *PreparedStatement, arguments ...interface{}
 
 		switch arg := arguments[i].(type) {
 		case BinaryEncoder:
-			err = arg.EncodeBinary(wbuf, &ps.FieldDescriptions[i])
+			err = arg.EncodeBinary(wbuf, oid)
 		case TextEncoder:
 			var s string
 			var status byte
diff --git a/values.go b/values.go
index 1b8d6eab..403e0238 100644
--- a/values.go
+++ b/values.go
@@ -66,12 +66,12 @@ type TextEncoder interface {
 type BinaryEncoder interface {
 	// EncodeBinary writes the binary value to w.
 	//
-	// EncodeBinary MUST check fd.DataType to see if the parameter data type is
+	// EncodeBinary MUST check oid to see if the parameter data type is
 	// compatible. If this is not done, the PostgreSQL server may detect the
 	// error if the expected data size or format of the encoded data does not
 	// match. But if the encoded data is a valid representation of the data type
 	// PostgreSQL expects such as date and int4, incorrect data may be stored.
-	EncodeBinary(w *WriteBuf, fd *FieldDescription) error
+	EncodeBinary(w *WriteBuf, oid Oid) error
 }
 
 // NullFloat32 represents an float4 that may be null.
@@ -103,9 +103,9 @@ func (n NullFloat32) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullFloat32) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != Float4Oid {
-		return SerializationError(fmt.Sprintf("NullFloat32.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullFloat32) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != Float4Oid {
+		return SerializationError(fmt.Sprintf("NullFloat32.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -145,9 +145,9 @@ func (n NullFloat64) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullFloat64) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != Float8Oid {
-		return SerializationError(fmt.Sprintf("NullFloat64.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullFloat64) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != Float8Oid {
+		return SerializationError(fmt.Sprintf("NullFloat64.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -216,9 +216,9 @@ func (n NullInt16) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullInt16) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != Int2Oid {
-		return SerializationError(fmt.Sprintf("NullInt16.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullInt16) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != Int2Oid {
+		return SerializationError(fmt.Sprintf("NullInt16.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -258,9 +258,9 @@ func (n NullInt32) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullInt32) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != Int4Oid {
-		return SerializationError(fmt.Sprintf("NullInt32.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullInt32) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != Int4Oid {
+		return SerializationError(fmt.Sprintf("NullInt32.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -300,9 +300,9 @@ func (n NullInt64) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullInt64) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != Int8Oid {
-		return SerializationError(fmt.Sprintf("NullInt64.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullInt64) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != Int8Oid {
+		return SerializationError(fmt.Sprintf("NullInt64.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -342,9 +342,9 @@ func (n NullBool) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullBool) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != BoolOid {
-		return SerializationError(fmt.Sprintf("NullBool.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullBool) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != BoolOid {
+		return SerializationError(fmt.Sprintf("NullBool.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
@@ -390,9 +390,9 @@ func (n NullTime) EncodeText() (string, byte, error) {
 	}
 }
 
-func (n NullTime) EncodeBinary(w *WriteBuf, fd *FieldDescription) error {
-	if fd.DataType != TimestampTzOid {
-		return SerializationError(fmt.Sprintf("NullTime.EncodeBinary cannot encode into OID %d", fd.DataType))
+func (n NullTime) EncodeBinary(w *WriteBuf, oid Oid) error {
+	if oid != TimestampTzOid {
+		return SerializationError(fmt.Sprintf("NullTime.EncodeBinary cannot encode into OID %d", oid))
 	}
 
 	if !n.Valid {
diff --git a/values_test.go b/values_test.go
index fba87f56..6bc9c1a3 100644
--- a/values_test.go
+++ b/values_test.go
@@ -200,6 +200,7 @@ func TestNullX(t *testing.T) {
 		{"select $1::bool", []interface{}{pgx.NullBool{Bool: true, Valid: false}}, []interface{}{&actual.b}, allTypes{b: pgx.NullBool{Bool: false, Valid: false}}},
 		{"select $1::timestamptz", []interface{}{pgx.NullTime{Time: time.Unix(123, 5000), Valid: true}}, []interface{}{&actual.t}, allTypes{t: pgx.NullTime{Time: time.Unix(123, 5000), Valid: true}}},
 		{"select $1::timestamptz", []interface{}{pgx.NullTime{Time: time.Unix(123, 5000), Valid: false}}, []interface{}{&actual.b}, allTypes{t: pgx.NullTime{Time: time.Time{}, Valid: false}}},
+		{"select 42::int4, $1::float8", []interface{}{pgx.NullFloat64{Float64: 1.23, Valid: true}}, []interface{}{&actual.i32, &actual.f64}, allTypes{i32: pgx.NullInt32{Int32: 42, Valid: true}, f64: pgx.NullFloat64{Float64: 1.23, Valid: true}}},
 	}
 
 	for i, tt := range tests {