diff --git a/doc/jvm/index.md b/doc/jvm/index.md
index 625a57063..a6e731c54 100644
--- a/doc/jvm/index.md
+++ b/doc/jvm/index.md
@@ -9,7 +9,9 @@ Installation
 ------------
 Currently, XGBoost4J only support installation from source. Building XGBoost4J using Maven requires Maven 3 or newer and Java 7+. 
 
-To install XGBoost4J, it is as simple as run `mvn package` under jvm-packages. 
+Before you install XGBoost4J, you need to define environment variable `JAVA_HOME` as your JDK directory to ensure that your compiler can find `jni.h` correctly, since XGBoost4J relies on JNI to implement the interaction between the JVM and native libraries.
+
+After your `JAVA_HOME` is defined correctly, it is as simple as run `mvn package` under jvm-packages directory to install XGBoost4J.
 
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