diff --git a/wscript b/wscript
index e2c946b..7f33a8e 100644
--- a/wscript
+++ b/wscript
@@ -46,6 +46,7 @@
     boost_libs='system'
     if conf.options.with_tests:
         conf.env['WITH_TESTS'] = 1
+        conf.define('WITH_TESTS', 1);
         boost_libs+=' unit_test_framework'
 
     conf.check_boost(lib=boost_libs)