diff --git a/src_main/system/pisystemmonitor.cpp b/src_main/system/pisystemmonitor.cpp
index 7f734fdb..9ac44135 100755
--- a/src_main/system/pisystemmonitor.cpp
+++ b/src_main/system/pisystemmonitor.cpp
@@ -34,6 +34,7 @@
 #endif
 
 
+#ifndef FREERTOS
 PRIVATE_DEFINITION_START(PISystemMonitor)
 #ifndef WINDOWS
 #  ifdef MAC_OS
@@ -51,6 +52,7 @@ PRIVATE_DEFINITION_START(PISystemMonitor)
 	PITimeMeasurer tm;
 #endif
 PRIVATE_DEFINITION_END(PISystemMonitor)
+#endif
 
 
 PISystemMonitor::PISystemMonitor(): PIThread() {
diff --git a/src_main/system/pisystemmonitor.h b/src_main/system/pisystemmonitor.h
index 1068027a..0dbcc71b 100755
--- a/src_main/system/pisystemmonitor.h
+++ b/src_main/system/pisystemmonitor.h
@@ -92,8 +92,9 @@ private:
 	PIMap<llong, PIString> tbid;
 	bool self_;
 	int pID_, page_size, cpu_count, cycle;
+#ifndef FREERTOS
 	PRIVATE_DECLARATION
-
+#endif
 };
 
 inline PICout operator <<(PICout s, const PISystemMonitor::ThreadStats & v) {