diff --git a/expression/builtin_info.go b/expression/builtin_info.go
index 1ea390336a2e6..e001bb549611c 100644
--- a/expression/builtin_info.go
+++ b/expression/builtin_info.go
@@ -626,12 +626,13 @@ func (b *builtinTiDBDecodeKeySig) evalString(row chunk.Row) (string, bool, error
 	if isNull || err != nil {
 		return "", isNull, err
 	}
-	return decodeKey(s), false, nil
+	return decodeKey(b.ctx, s), false, nil
 }
 
-func decodeKey(s string) string {
+func decodeKey(ctx sessionctx.Context, s string) string {
 	key, err := hex.DecodeString(s)
 	if err != nil {
+		ctx.GetSessionVars().StmtCtx.AppendWarning(errors.New("the key is a invalid record/index key"))
 		return s
 	}
 	// Auto decode byte if needs.
@@ -652,5 +653,6 @@ func decodeKey(s string) string {
 	}
 
 	// TODO: try to decode other type key.
+	ctx.GetSessionVars().StmtCtx.AppendWarning(errors.New("the key is a invalid record/index key"))
 	return s
 }
diff --git a/expression/integration_test.go b/expression/integration_test.go
index c990e95b03eea..006e1b31a7015 100755
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -4131,6 +4131,13 @@ func (s *testIntegrationSuite) TestTiDBInternalFunc(c *C) {
 
 	result = tk.MustQuery("select tidb_decode_key( '74800000000000019B5F698000000000000001015257303100000000FB013736383232313130FF3900000000000000F8010000000000000000F7' )")
 	result.Check(testkit.Rows("tableID=411, indexID=1, indexValues=015257303100000000FB013736383232313130FF3900000000000000F8010000000000000000F7"))
+
+	// Test invalid record/index key.
+	result = tk.MustQuery("select tidb_decode_key( '7480000000000000FF2E5F728000000011FFE1A3000000000000' )")
+	result.Check(testkit.Rows("7480000000000000FF2E5F728000000011FFE1A3000000000000"))
+	warns := tk.Se.GetSessionVars().StmtCtx.GetWarnings()
+	c.Assert(warns, HasLen, 1)
+	c.Assert(warns[0].Err.Error(), Equals, "the key is a invalid record/index key")
 }
 
 func newStoreWithBootstrap() (kv.Storage, *domain.Domain, error) {