diff --git a/ReadMe.md b/ReadMe.md
index f690dd03bd1..13b92d33f6c 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -17,7 +17,7 @@ Welcome to [Kotlin](http://www.jetbrains.com/kotlin)! Some handy links:
 
 ## Building
 
-To build this project, first time you try to build you need to run this:
+To build this project, first time you try to build you need to run this (requires Apache Ant 1.8 or higher):
 
     ant -f update_dependencies.xml