diff --git a/modules/fdlibm/src/fdlibm.h b/modules/fdlibm/src/fdlibm.h
--- a/modules/fdlibm/src/fdlibm.h
+++ b/modules/fdlibm/src/fdlibm.h
@@ -9,18 +9,18 @@
  * ====================================================
  */
 
 /*
  * from: @(#)fdlibm.h 5.1 93/09/24
  * $FreeBSD$
  */
 
-#ifndef _MATH_H_
-#define	_MATH_H_
+#ifndef mozilla_imported_fdlibm_h
+#define mozilla_imported_fdlibm_h
 
 double	acos(double);
 double	asin(double);
 double	atan(double);
 double	atan2(double, double);
 
 double	cosh(double);
 double	sinh(double);
@@ -52,9 +52,9 @@ double	scalbn(double, int);
 
 float	ceilf(float);
 float	floorf(float);
 
 float	nearbyintf(float);
 float	rintf(float);
 float	truncf(float);
 
-#endif /* !_MATH_H_ */
+#endif /* mozilla_imported_fdlibm_h */