--- a/libc/sysdeps/linux/common/bits/mathcalls.h
+++ b/libc/sysdeps/linux/common/bits/mathcalls.h
@@ -237,8 +237,7 @@ __END_NAMESPACE_C99
 
 
 /* Return nonzero if VALUE is not a number.  */
-/* DELETE? __MATHDECL_PRIV adds another "__": so this is "____isnan"???! */
-/*__MATHDECL_PRIV (int,__isnan,, (_Mdouble_ __value), (__const__))*/
+__MATHDECL_PRIV (int,isnan,, (_Mdouble_ __value), (__const__));
 
 #if defined __USE_MISC || defined __USE_XOPEN
 /* Return nonzero if VALUE is not a number.  */