diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
index cf949394e7077..aba6aa3475cca 100644
--- a/expression/expr_to_pb_test.go
+++ b/expression/expr_to_pb_test.go
@@ -1386,11 +1386,6 @@ func TestExprPushDownToTiKV(t *testing.T) {
 			retType:      types.NewFieldType(mysql.TypeString),
 			args:         []Expression{stringColumn, stringColumn, intColumn},
 		},
-		{
-			functionName: ast.Instr,
-			retType:      types.NewFieldType(mysql.TypeInt24),
-			args:         []Expression{stringColumn, stringColumn},
-		},
 		{
 			functionName: ast.Quote,
 			retType:      types.NewFieldType(mysql.TypeString),
diff --git a/expression/expression.go b/expression/expression.go
index fe56ff5520883..656447931a8f0 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -970,7 +970,7 @@ func scalarExprSupportedByTiKV(sf *ScalarFunction) bool {
 		// string functions.
 		ast.Bin, ast.Unhex, ast.Locate, ast.Ord, ast.Lpad, ast.Rpad,
 		ast.Trim, ast.FromBase64, ast.ToBase64, ast.Upper, ast.Lower, ast.InsertFunc,
-		ast.MakeSet, ast.SubstringIndex, ast.Instr, ast.Quote, ast.Oct,
+		ast.MakeSet, ast.SubstringIndex /* ast.Instr */, ast.Quote, ast.Oct,
 		ast.FindInSet, ast.Repeat,
 		ast.Length, ast.BitLength, ast.Concat, ast.ConcatWS, ast.Replace, ast.ASCII, ast.Hex,
 		ast.Reverse, ast.LTrim, ast.RTrim, ast.Strcmp, ast.Space, ast.Elt, ast.Field,
diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
index 49661c3119ab6..c28014215a4f8 100644
--- a/planner/core/integration_test.go
+++ b/planner/core/integration_test.go
@@ -2912,10 +2912,6 @@ func TestScalarFunctionPushDown(t *testing.T) {
 	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where substring_index(c,c,1)").
 		CheckAt([]int{0, 3, 6}, rows)
 
-	rows[1][2] = "instr(test.t.c, test.t.c)"
-	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where instr(c,c)").
-		CheckAt([]int{0, 3, 6}, rows)
-
 	rows[1][2] = "quote(test.t.c)"
 	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where quote(c)").
 		CheckAt([]int{0, 3, 6}, rows)