diff --git a/tablecodec/tablecodec.go b/tablecodec/tablecodec.go
index 9179955af674f..7c480d4ab8751 100644
--- a/tablecodec/tablecodec.go
+++ b/tablecodec/tablecodec.go
@@ -512,11 +512,11 @@ func unflatten(datum types.Datum, ft *types.FieldType, loc *time.Location) (type
 	case mysql.TypeFloat:
 		datum.SetFloat32(float32(datum.GetFloat64()))
 		return datum, nil
-	case mysql.TypeVarchar, mysql.TypeString, mysql.TypeVarString:
+	case mysql.TypeVarchar, mysql.TypeString, mysql.TypeVarString, mysql.TypeTinyBlob,
+		mysql.TypeMediumBlob, mysql.TypeBlob, mysql.TypeLongBlob:
 		datum.SetString(datum.GetString(), ft.Collate)
 	case mysql.TypeTiny, mysql.TypeShort, mysql.TypeYear, mysql.TypeInt24,
-		mysql.TypeLong, mysql.TypeLonglong, mysql.TypeDouble, mysql.TypeTinyBlob,
-		mysql.TypeMediumBlob, mysql.TypeBlob, mysql.TypeLongBlob:
+		mysql.TypeLong, mysql.TypeLonglong, mysql.TypeDouble:
 		return datum, nil
 	case mysql.TypeDate, mysql.TypeDatetime, mysql.TypeTimestamp:
 		t := types.NewTime(types.ZeroCoreTime, ft.Tp, int8(ft.Decimal))
diff --git a/tablecodec/tablecodec_test.go b/tablecodec/tablecodec_test.go
index b56c3cd6b9901..3a27b01ae8be9 100644
--- a/tablecodec/tablecodec_test.go
+++ b/tablecodec/tablecodec_test.go
@@ -175,6 +175,16 @@ func (s *testTableCodecSuite) TestUnflattenDatums(c *C) {
 	cmp, err := input[0].CompareDatum(sc, &output[0])
 	c.Assert(err, IsNil)
 	c.Assert(cmp, Equals, 0)
+
+	input = []types.Datum{types.NewCollationStringDatum("aaa", "utf8mb4_unicode_ci", 0)}
+	tps = []*types.FieldType{types.NewFieldType(mysql.TypeBlob)}
+	tps[0].Collate = "utf8mb4_unicode_ci"
+	output, err = UnflattenDatums(input, tps, sc.TimeZone)
+	c.Assert(err, IsNil)
+	cmp, err = input[0].CompareDatum(sc, &output[0])
+	c.Assert(err, IsNil)
+	c.Assert(cmp, Equals, 0)
+	c.Assert(output[0].Collation(), Equals, "utf8mb4_unicode_ci")
 }
 
 func (s *testTableCodecSuite) TestTimeCodec(c *C) {