diff --git a/addon-modules/README b/addon-modules/README
index 19f268fa52..b5bf2e007e 100644
--- a/addon-modules/README
+++ b/addon-modules/README
@@ -3,3 +3,7 @@ In this directory you can place addon modules for OpenSim
 Each module should be in it's own tree and the root of the tree
 should contain a file named "prebuild.xml", which will be included in the
 main prebuild file.
+
+The prebuild.xml should only contain <Project> and associated child tags.  
+The <?xml>, <Prebuild>, <Solution> and <Configuration> tags should not be 
+included since the add-on modules prebuild.xml will be inserted directly into the main prebuild.xml