diff --git a/samples/wscript b/samples/wscript
index 5286f56c9..deba5598e 100644
--- a/samples/wscript
+++ b/samples/wscript
@@ -19,7 +19,7 @@ def build(bld):
     obj = bld.create_ns3_program('main-test')
     obj.source = 'main-test.cc'
 
-    if bld.env['ENABLE_THREADING']:
+    if bld.env['ENABLE_THREADING'] and bld.env["ENABLE_REAL_TIME"]:
         obj = bld.create_ns3_program('main-test-sync')
         obj.source = 'main-test-sync.cc'