--- a/Sources/Core/IOData/Generic/inputsource_file.cpp
+++ b/Sources/Core/IOData/Generic/inputsource_file.cpp
@@ -32,6 +32,7 @@
 #ifdef WIN32
 #include <direct.h>
 #endif
+#include <unistd.h>
 #include <cstring>
 #include <API/Core/IOData/inputsource_file.h>