diff --git a/Contrib/System/Source/Plugin.h b/Contrib/System/Source/Plugin.h
index e6a2df28..b6ffb3de 100644
--- a/Contrib/System/Source/Plugin.h
+++ b/Contrib/System/Source/Plugin.h
@@ -1,4 +1,5 @@
-#pragma once
+#ifndef ___PLUGIN__H___
+#define ___PLUGIN__H___
 
 typedef struct _stack_t {
   struct _stack_t *next;
@@ -64,3 +65,5 @@ extern HWND g_hwndParent;
 extern int g_stringsize;
 extern stack_t **g_stacktop;
 extern char *g_variables;
+
+#endif
diff --git a/Contrib/System/Source/System.h b/Contrib/System/Source/System.h
index 303e8ac0..96f4cd82 100644
--- a/Contrib/System/Source/System.h
+++ b/Contrib/System/Source/System.h
@@ -1,10 +1,12 @@
+#ifndef ___SYSTEM__H___
+#define ___SYSTEM__H___
+
 // The following ifdef block is the standard way of creating macros which make exporting 
 // from a DLL simpler. All files within this DLL are compiled with the SYSTEM_EXPORTS
 // symbol defined on the command line. this symbol should not be defined on any project
 // that uses this DLL. This way any other project whose source files include this file see 
 // SYSTEM_API functions as being imported from a DLL, whereas this DLL sees symbols
 // defined with this macro as being exported.
-#pragma once
 
 #ifdef SYSTEM_EXPORTS
 #define SYSTEM_API __declspec(dllexport)
@@ -103,3 +105,5 @@ extern SystemProc *CallProc(SystemProc *proc);
 extern SystemProc *CallBack(SystemProc *proc);
 extern SystemProc *RealCallBack();
 extern void CallStruct(SystemProc *proc);
+
+#endif