diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 6607ea2..6f268bb 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -8,7 +8,7 @@
 
 import testing ;
 
-local gcc-flags = -Wsign-promo -Wconversion -Wsign-conversion -Wshadow ;
+local gcc-flags = -Wsign-promo -Wconversion -Wsign-conversion -Wshadow -Wundef ;
 
 project
     : requirements
@@ -23,7 +23,6 @@ project
         <toolset>clang:<cxxflags>$(gcc-flags)
     ;
 
-
 run throw_exception_test.cpp ;
 run throw_exception_no_exceptions_test.cpp ;
 run throw_exception_no_integration_test.cpp ;