diff --git a/build.properties b/build.properties
index 379557244..b84371891 100644
--- a/build.properties
+++ b/build.properties
@@ -1,5 +1,9 @@
 version=2.1
 
+# These properties are mostly needed for the top-level javadoc target. android-home is required by
+# android-integration/, tomcat-home is needed by zxingorg/, GWT-home is needed by zxing.appspot.com/ .
+# If you aren't building those targets you need not set anything here.
+
 # Set this to the location where you installed the Android SDK.
 #android-home=C:\\Program Files\\android-sdk-windows
 #android-home=/usr/local/android-sdk