diff --git a/v2/build/project.jam b/v2/build/project.jam
index e27791380..3f0e885c5 100644
--- a/v2/build/project.jam
+++ b/v2/build/project.jam
@@ -726,7 +726,7 @@ rule use ( id : location )
           && $($(id).jamfile-module) != $(project-module)
         {
             errors.user-error 
-              "Attempt to redeclare already existing project id" ;
+              "Attempt to redeclare already existing project id '$(id)'" ;
         }                  
         $(id).jamfile-module = $(project-module) ;
     }