diff --git Source/Engine/FastLM.cpp Source/Engine/FastLM.cpp
index 9977d31..36b5264 100644
--- Source/Engine/FastLM.cpp
+++ Source/Engine/FastLM.cpp
@@ -29,6 +29,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <fstream>
 
 using namespace Formosa::Gramambular;