diff --git a/src/wscript b/src/wscript
index 1ebbc2bf7..e8e2938ec 100644
--- a/src/wscript
+++ b/src/wscript
@@ -51,7 +51,7 @@ def configure(conf):
     conf.sub_config('contrib')
 
     blddir = os.path.abspath(os.path.join(conf.m_blddir, conf.env.variant()))
-    conf.env['NS3_MODULE_PATH'] = [blddir]
+    conf.env.append_value('NS3_MODULE_PATH', blddir)
     if Params.g_options.enable_rpath:
         conf.env.append_value('RPATH', '-Wl,-rpath=%s' % (os.path.join(blddir),))