diff --git a/src/internet-stack/wscript b/src/internet-stack/wscript
index 23bbb89fb..fa5a62580 100644
--- a/src/internet-stack/wscript
+++ b/src/internet-stack/wscript
@@ -75,7 +75,7 @@ def configure(conf):
     ok = False
     if arch == 'x86_64' or arch == 'i686' or arch == 'i586' or arch == 'i486' or arch == 'i386':
         conf.env['NSC_ENABLED'] = 'yes'
-        conf.define('NETWORK_SIMULATION_CRADLE', 1)
+        conf.env.append_value('CXXDEFINES', 'NETWORK_SIMULATION_CRADLE')
         e = conf.create_library_configurator()
         e.mandatory = True
         e.name = 'dl'
diff --git a/src/simulator/wscript b/src/simulator/wscript
index 90503fd2c..aaa7fb1de 100644
--- a/src/simulator/wscript
+++ b/src/simulator/wscript
@@ -16,7 +16,7 @@ def set_options(opt):
 
 def configure(conf):
     if Params.g_options.high_precision_as_double:
-        conf.add_define('USE_HIGH_PRECISION_DOUBLE', 1)
+        conf.define('USE_HIGH_PRECISION_DOUBLE', 1)
         conf.env['USE_HIGH_PRECISION_DOUBLE'] = 1
         highprec = 'long double'
     else: