diff -Naur gcc-11.1.0/libstdc++-v3/include/c_compatibility/fenv.h gcc-11.1.0.serenity/libstdc++-v3/include/c_compatibility/fenv.h
--- gcc-11.1.0/libstdc++-v3/include/c_compatibility/fenv.h	2021-04-27 12:00:16.000000000 +0200
+++ gcc-11.1.0.serenity/libstdc++-v3/include/c_compatibility/fenv.h	2021-04-27 18:19:15.749373118 +0200
@@ -26,8 +26,8 @@
  *  This is a Standard C++ Library header.
  */
 
-#ifndef _GLIBCXX_FENV_H
-#define _GLIBCXX_FENV_H 1
+#ifndef _GLIBCXX_PORT_FENV_H
+#define _GLIBCXX_PORT_FENV_H 1
 
 #pragma GCC system_header
 
@@ -78,4 +78,4 @@
 
 #endif // C++11
 
-#endif // _GLIBCXX_FENV_H
+#endif // _GLIBCXX_PORT_FENV_H