diff --git a/libc/include/math.h b/libc/include/math.h
index 7efc83a..8c084b2 100644
--- a/libc/include/math.h
+++ b/libc/include/math.h
@@ -10,12 +10,10 @@
  */
 
 /*
- * from: @(#)fdlibm.h 5.1 93/09/24
- * $FreeBSD$
+ * Originally based on fdlibm.h 5.1 via FreeBSD.
  */
 
-#ifndef _MATH_H_
-#define _MATH_H_
+#pragma once
 
 #include <sys/cdefs.h>
 #include <limits.h>
@@ -408,5 +406,3 @@
 #endif
 
 __END_DECLS
-
-#endif