Index: src/core/datadir.cpp
--- src/core/datadir.cpp.orig	2016-10-26 21:35:33.000000000 +0200
+++ src/core/datadir.cpp	2016-11-03 07:39:21.626046690 +0100
@@ -28,6 +28,7 @@
 #include <string>
 #include <fstream>
 #include <vector>
+#include <cstdlib>
 #include "platform_fs.h"
 
 #include "datadir.h"
Index: src/core/rtfgenerator.cpp
--- src/core/rtfgenerator.cpp.orig	2016-10-29 17:46:00.000000000 +0200
+++ src/core/rtfgenerator.cpp	2016-11-03 07:40:11.406063633 +0100
@@ -32,6 +32,14 @@
 #include "version.h"
 #include "rtfgenerator.h"
 
+#include <sstream>
+
+template <typename T> std::string my_to_string(const T& n) {
+    std::ostringstream stm;
+    stm << n;
+    return stm.str();
+}
+
 namespace highlight
 {
 
@@ -276,7 +284,7 @@
 
         if (!utf8SeqLen) {
             string m ( "\\u" );
-            m += to_string(utf16Char);
+            m += my_to_string(utf16Char);
             m += '?';
             utf16Char=0L;
             return m;
