--- src/gengine/OptionAgent.cpp
+++ src/gengine/OptionAgent.cpp
@@ -25,6 +25,7 @@
 
 #include <string.h> //strlen
 #include <locale.h> //setlocale
+#include <cstdlib> //getenv
 
 #ifndef LC_MESSAGES
 #define LC_MESSAGES LC_CTYPE
--- src/gengine/StringTool.cpp
+++ src/gengine/StringTool.cpp
@@ -9,6 +9,7 @@
 #include "StringTool.h"
 
 #include <sstream>
+#include <cstdlib>
 
 //-----------------------------------------------------------------
 /**
--- src/level/Landslip.cpp
+++ src/level/Landslip.cpp
@@ -10,6 +10,7 @@
 
 #include "Rules.h"
 #include "minmax.h"
+#include <cstring>
 
 //-----------------------------------------------------------------
     Landslip::Landslip(const ModelList &models)