diff --git a/include/mimalloc-atomic.h b/include/mimalloc-atomic.h
index 2ca568ef..fb97f59c 100644
--- a/include/mimalloc-atomic.h
+++ b/include/mimalloc-atomic.h
@@ -5,8 +5,8 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 #pragma once
-#ifndef __MIMALLOC_ATOMIC_H
-#define __MIMALLOC_ATOMIC_H
+#ifndef MIMALLOC_ATOMIC_H
+#define MIMALLOC_ATOMIC_H
 
 // ------------------------------------------------------
 // Atomics
diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index 160716d7..97abb4a3 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -5,8 +5,8 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 #pragma once
-#ifndef __MIMALLOC_INTERNAL_H
-#define __MIMALLOC_INTERNAL_H
+#ifndef MIMALLOC_INTERNAL_H
+#define MIMALLOC_INTERNAL_H
 
 #include "mimalloc-types.h"
 
diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index c660897e..de6b21d5 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -5,8 +5,8 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 #pragma once
-#ifndef __MIMALLOC_TYPES_H
-#define __MIMALLOC_TYPES_H
+#ifndef MIMALLOC_TYPES_H
+#define MIMALLOC_TYPES_H
 
 #include <stdlib.h>   // size_t etc.
 #include <stddef.h>   // ptrdiff_t
diff --git a/include/mimalloc.h b/include/mimalloc.h
index b5fd6f96..51f7ce1b 100644
--- a/include/mimalloc.h
+++ b/include/mimalloc.h
@@ -5,8 +5,8 @@ terms of the MIT license. A copy of the license can be found in the file
 "LICENSE" at the root of this distribution.
 -----------------------------------------------------------------------------*/
 #pragma once
-#ifndef __MIMALLOC_H
-#define __MIMALLOC_H
+#ifndef MIMALLOC_H
+#define MIMALLOC_H
 
 #define MI_MALLOC_VERSION 100   // major + 2 digits minor