diff --git a/build.gradle b/build.gradle
index 9d2c5df25f..415ec67a96 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,6 +4,7 @@ buildscript {
     ext.kotlin_version = '1.5.0-release-764'
     ext {
         // kotlin 1.5.0 prevents travis from pass
+        // remove @kotlin.ExperimentalStdlibApi everywhere when upgrade
         kotlin_version = '1.4.32'
         coreVersion = '1.5.0'
         rxjava_version = '2.2.21'