diff --git a/xc-tutor.c b/xc-tutor.c
index 5a69d52..941efd4 100644
--- a/xc-tutor.c
+++ b/xc-tutor.c
@@ -6,6 +6,8 @@
 #include <memory.h>
 #include <string.h>
 #include <stdint.h>
+#include <fcntl.h>
+#include <unistd.h>
 #define int intptr_t
 
 int token;                    // current token
diff --git a/xc.c b/xc.c
index 810c2a5..0c44a42 100644
--- a/xc.c
+++ b/xc.c
@@ -2,6 +2,8 @@
 #include <stdlib.h>
 #include <memory.h>
 #include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
 #define int long long // to work with 64bit address
 
 int debug;    // print the executed instructions