diff --git a/int.h b/int.h
index 19bcfef..f7bb71b 100644
--- a/int.h
+++ b/int.h
@@ -1,3 +1,6 @@
+#ifndef MINIMALINT_H
+#define MINIMALINT_H
+
 #if defined(__x86_64__) || defined(__aarch64__)
 #define __WORDSIZE 64
 #elif defined(__mips__)
@@ -55,3 +58,4 @@ typedef uint32_t uintptr_t;
 
 //TODO:
 //#ifdef __SIZEOF_SIZE_T__
+#endif // !MINIMALINT_H
diff --git a/sys.h b/sys.h
index e3bed1d..8d2237f 100644
--- a/sys.h
+++ b/sys.h
@@ -1,4 +1,6 @@
 #ifndef MINIMALSYS_H
+#define MINIMALSYS_H
+
 #include "int.h"
 
 void exit(int8_t status);