diff --git a/expression/builtin_cast.go b/expression/builtin_cast.go
index a8a5323583c22..899035d5e74b2 100644
--- a/expression/builtin_cast.go
+++ b/expression/builtin_cast.go
@@ -290,6 +290,9 @@ func (c *castAsStringFunctionClass) getFunction(ctx sessionctx.Context, args []E
 	argTp := args[0].GetType().EvalType()
 	switch argTp {
 	case types.ETInt:
+		if bf.tp.Flen == types.UnspecifiedLength {
+			bf.tp.Flen = args[0].GetType().Flen
+		}
 		sig = &builtinCastIntAsStringSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_CastIntAsString)
 	case types.ETReal:
diff --git a/expression/integration_test.go b/expression/integration_test.go
index e26e8d850ec17..39f09359b68a5 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -10267,6 +10267,19 @@ func (s *testIntegrationSuite) TestIssue29417(c *C) {
 	tk.MustQuery("select concat(f1) from t1;").Check(testkit.Rows("-0.12345"))
 }
 
+func (s *testIntegrationSuite) TestIssue29513(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustQuery("select '123' union select cast(45678 as char);").Sort().Check(testkit.Rows("123", "45678"))
+	tk.MustQuery("select '123' union select cast(45678 as char(2));").Sort().Check(testkit.Rows("123", "45"))
+
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int);")
+	tk.MustExec("insert into t values(45678);")
+	tk.MustQuery("select '123' union select cast(a as char) from t;").Sort().Check(testkit.Rows("123", "45678"))
+	tk.MustQuery("select '123' union select cast(a as char(2)) from t;").Sort().Check(testkit.Rows("123", "45"))
+}
+
 func (s *testIntegrationSuite) TestIssue28643(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
diff --git a/expression/typeinfer_test.go b/expression/typeinfer_test.go
index 4293241a5ffbd..30ca35f6bdd20 100644
--- a/expression/typeinfer_test.go
+++ b/expression/typeinfer_test.go
@@ -180,9 +180,9 @@ func (s *testInferTypeSuite) createTestCase4Constants() []typeInferTestCase {
 
 func (s *testInferTypeSuite) createTestCase4Cast() []typeInferTestCase {
 	return []typeInferTestCase{
-		{"CAST(c_int_d AS BINARY)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, -1, -1}, // TODO: Flen should be 11.
+		{"CAST(c_int_d AS BINARY)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 11, -1},
 		{"CAST(c_int_d AS BINARY(5))", mysql.TypeString, charset.CharsetBin, mysql.BinaryFlag, 5, -1},
-		{"CAST(c_int_d AS CHAR)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, -1, -1}, // TODO: Flen should be 11.
+		{"CAST(c_int_d AS CHAR)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 11, -1},
 		{"CAST(c_int_d AS CHAR(5))", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 5, -1},
 		{"CAST(c_int_d AS DATE)", mysql.TypeDate, charset.CharsetBin, mysql.BinaryFlag, 10, 0},
 		{"CAST(c_int_d AS DATETIME)", mysql.TypeDatetime, charset.CharsetBin, mysql.BinaryFlag, 19, 0},
@@ -405,8 +405,8 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 
 		{"reverse(c_int_d      )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
 		{"reverse(c_bigint_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
-		{"reverse(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, -1, types.UnspecifiedLength},
-		{"reverse(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, -1, types.UnspecifiedLength},
+		{"reverse(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, types.UnspecifiedLength, types.UnspecifiedLength},
+		{"reverse(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, types.UnspecifiedLength, types.UnspecifiedLength},
 		{"reverse(c_decimal    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 9, types.UnspecifiedLength},
 		{"reverse(c_char       )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
 		{"reverse(c_varchar    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},