diff --git a/iso646.h b/iso646.h
index 70a939d..599705e 100644
--- a/iso646.h
+++ b/iso646.h
@@ -1,5 +1,5 @@
-#ifndef __ISO646_H__
-#define __ISO646_H__
+#ifndef _ISO646_H
+#define _ISO646_H 1
 
 #define and &&
 #define and_eq &=
diff --git a/stdalign.h b/stdalign.h
index 9786e16..b2e53a4 100644
--- a/stdalign.h
+++ b/stdalign.h
@@ -1,8 +1,8 @@
-#ifndef __STDALIGN_H__
-#define __STDALIGN_H__
+#ifndef _STDALIGN_H
+#define _STDALIGN_H 1
 
-#define alignas(a) _Alignas(a)
-#define alignof(t) _Alignof(t)
+#define alignas _Alignas
+#define alignof _Alignof
 
 #define __alignas_is_defined 1
 #define __alignof_is_defined 1
diff --git a/stdarg.h b/stdarg.h
index 6ed7e6b..fa243e0 100644
--- a/stdarg.h
+++ b/stdarg.h
@@ -1,5 +1,5 @@
-#ifndef __STDARG_H__
-#define __STDARG_H__
+#ifndef _STDARG_H
+#define _STDARG_H 1
 
 typedef __builtin_va_list va_list;
 
diff --git a/stdbool.h b/stdbool.h
index 001f937..bb2328c 100644
--- a/stdbool.h
+++ b/stdbool.h
@@ -1,5 +1,5 @@
-#ifndef __STDBOOL_H__
-#define __STDBOOL_H__
+#ifndef _STDBOOL_H
+#define _STDBOOL_H 1
 
 #define bool _Bool
 
diff --git a/stddef.h b/stddef.h
index 165e63b..4b85c13 100644
--- a/stddef.h
+++ b/stddef.h
@@ -1,5 +1,5 @@
-#ifndef __STDDEF_H__
-#define __STDDEF_H__
+#ifndef _STDDEF_H
+#define _STDDEF_H 1
 
 typedef __SIZE_TYPE__ size_t;
 typedef __PTRDIFF_TYPE__ ptrdiff_t;
diff --git a/stdint.h b/stdint.h
index f65c43d..5e15cbb 100644
--- a/stdint.h
+++ b/stdint.h
@@ -1,5 +1,5 @@
-#ifndef __STDINT_H__
-#define __STDINT_H__
+#ifndef _STDINT_H
+#define _STDINT_H 1
 
 typedef __UINT8_TYPE__ uint8_t;
 typedef __UINT16_TYPE__ uint16_t;
diff --git a/stdnoreturn.h b/stdnoreturn.h
index 7f263e7..9c2691f 100644
--- a/stdnoreturn.h
+++ b/stdnoreturn.h
@@ -1,5 +1,5 @@
-#ifndef __STDNORETURN_H__
-#define __STDNORETURN_H__
+#ifndef _STDNORETURN_H
+#define _STDNORETURN_H 1
 
 #define noreturn _Noreturn