diff --git a/expression/column.go b/expression/column.go
index c245bc10b3..e6f60dbf0c 100644
--- a/expression/column.go
+++ b/expression/column.go
@@ -237,7 +237,9 @@ func (col *Column) HashCode() []byte {
 	if len(col.hashcode) != 0 {
 		return col.hashcode
 	}
-	col.hashcode, _ = codec.EncodeValue(col.hashcode, types.NewIntDatum(int64(col.FromID)), types.NewIntDatum(int64(col.Position)))
+	col.hashcode = make([]byte, 0, 16)
+	col.hashcode = codec.EncodeInt(col.hashcode, int64(col.FromID))
+	col.hashcode = codec.EncodeInt(col.hashcode, int64(col.Position))
 	return col.hashcode
 }
 
diff --git a/expression/column_test.go b/expression/column_test.go
index 7d5b5a7b0f..0ad3698c38 100644
--- a/expression/column_test.go
+++ b/expression/column_test.go
@@ -93,6 +93,22 @@ func (s *testEvaluatorSuite) TestColumn(c *C) {
 	c.Assert(err, IsNil)
 }
 
+func (s *testEvaluatorSuite) TestColumnHashCode(c *C) {
+	defer testleak.AfterTest(c)()
+
+	col1 := &Column{
+		FromID:   1,
+		Position: 12,
+	}
+	c.Assert(col1.HashCode(), DeepEquals, []byte{0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc})
+
+	col2 := &Column{
+		FromID:   11,
+		Position: 2,
+	}
+	c.Assert(col2.HashCode(), DeepEquals, []byte{0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xb, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2})
+}
+
 func (s *testEvaluatorSuite) TestColumn2Expr(c *C) {
 	defer testleak.AfterTest(c)()
 
diff --git a/expression/scalar_function_test.go b/expression/scalar_function_test.go
index 6772f62e91..05d67912d8 100644
--- a/expression/scalar_function_test.go
+++ b/expression/scalar_function_test.go
@@ -38,7 +38,7 @@ func (s *testEvaluatorSuite) TestScalarFunction(c *C) {
 	c.Assert(res, DeepEquals, []byte{0x22, 0x6c, 0x74, 0x28, 0x66, 0x65, 0x69, 0x2e, 0x68, 0x61, 0x6e, 0x2c, 0x20, 0x31, 0x29, 0x22})
 	c.Assert(sf.IsCorrelated(), IsFalse)
 	c.Assert(sf.Decorrelate(nil).Equal(sf, s.ctx), IsTrue)
-	c.Assert(sf.HashCode(), DeepEquals, []byte{0x2, 0x8, 0x2, 0x4, 0x6c, 0x74, 0x2, 0x8, 0x8, 0x0, 0x8, 0x2, 0x2, 0x12, 0x5, 0xbf, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0})
+	c.Assert(sf.HashCode(), DeepEquals, []byte{0x2, 0x8, 0x2, 0x4, 0x6c, 0x74, 0x2, 0x20, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x2, 0x12, 0x5, 0xbf, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0})
 
 	sf = NewValuesFunc(0, types.NewFieldType(mysql.TypeLonglong), s.ctx)
 	newSf, ok := sf.Clone().(*ScalarFunction)