diff --git a/src/open9x.cpp b/src/open9x.cpp
index 56900c314..219c06fc6 100644
--- a/src/open9x.cpp
+++ b/src/open9x.cpp
@@ -31,7 +31,7 @@
  *
  */
 
-#if defined(PCBARM)
+#if defined(PCBARM) && !defined(SIMU)
 extern "C" {
 #include <CoOS.h>
 }