diff --git a/executor/statement_context_test.go b/executor/statement_context_test.go
new file mode 100644
index 0000000000000..6f6f2f44068d1
--- /dev/null
+++ b/executor/statement_context_test.go
@@ -0,0 +1,34 @@
+// Copyright 2016 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package executor_test
+
+import (
+	. "github.com/pingcap/check"
+	"github.com/pingcap/tidb/terror"
+	"github.com/pingcap/tidb/util/testkit"
+	"github.com/pingcap/tidb/util/types"
+)
+
+func (s *testSuite) TestStatementContext(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("create table sc (a int)")
+	tk.MustExec("insert sc values (1), (2)")
+	tk.MustQuery("select * from sc where a > cast(1.1 as decimal)").Check(testkit.Rows("2"))
+	_, err := tk.Exec("update sc set a = 4 where a > cast(1.1 as decimal)")
+	c.Check(terror.ErrorEqual(err, types.ErrTruncated), IsTrue)
+	tk.MustExec("set sql_mode = 0")
+	tk.MustExec("update sc set a = 3 where a > cast(1.1 as decimal)")
+	tk.MustQuery("select * from sc").Check(testkit.Rows("1", "3"))
+}
diff --git a/util/types/convert_test.go b/util/types/convert_test.go
index 97a2e8d77effa..ad1f370f76cec 100644
--- a/util/types/convert_test.go
+++ b/util/types/convert_test.go
@@ -39,6 +39,7 @@ type invalidMockType struct {
 func Convert(val interface{}, target *FieldType) (v interface{}, err error) {
 	d := NewDatum(val)
 	sc := new(variable.StatementContext)
+	sc.TruncateAsError = true
 	ret, err := d.ConvertTo(sc, target)
 	if err != nil {
 		return ret.GetValue(), errors.Trace(err)
diff --git a/util/types/datum.go b/util/types/datum.go
index 1372b1c2425d0..7548b50715dcc 100644
--- a/util/types/datum.go
+++ b/util/types/datum.go
@@ -664,7 +664,7 @@ func (d *Datum) ConvertTo(sc *variable.StatementContext, target *FieldType) (Dat
 	case mysql.TypeBit:
 		return d.convertToMysqlBit(target)
 	case mysql.TypeDecimal, mysql.TypeNewDecimal:
-		return d.convertToMysqlDecimal(target)
+		return d.convertToMysqlDecimal(sc, target)
 	case mysql.TypeYear:
 		return d.convertToMysqlYear(target)
 	case mysql.TypeEnum:
@@ -943,7 +943,7 @@ func (d *Datum) convertToMysqlDuration(target *FieldType) (Datum, error) {
 	return ret, nil
 }
 
-func (d *Datum) convertToMysqlDecimal(target *FieldType) (Datum, error) {
+func (d *Datum) convertToMysqlDecimal(sc *variable.StatementContext, target *FieldType) (Datum, error) {
 	var ret Datum
 	ret.SetLength(target.Flen)
 	ret.SetFrac(target.Decimal)
@@ -983,7 +983,9 @@ func (d *Datum) convertToMysqlDecimal(target *FieldType) (Datum, error) {
 		} else if frac != target.Decimal {
 			dec.Round(dec, target.Decimal)
 			if frac > target.Decimal {
-				err = errors.Trace(ErrTruncated)
+				if sc.TruncateAsError {
+					err = errors.Trace(ErrTruncated)
+				}
 			}
 		}
 	}