diff --git a/tools/include/nolibc/compiler.h b/tools/include/nolibc/compiler.h
index 1c410a62c528..b1239344d894 100644
--- a/tools/include/nolibc/compiler.h
+++ b/tools/include/nolibc/compiler.h
@@ -80,4 +80,10 @@
 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
 #define _NOLIBC_OPTIMIZER_HIDE_VAR(var)	__asm__ ("" : "+r" (var))
 
+#if __nolibc_has_feature(undefined_behavior_sanitizer)
+#  define __nolibc_no_sanitize_undefined __attribute__((no_sanitize("function")))
+#else
+#  define __nolibc_no_sanitize_undefined
+#endif
+
 #endif /* _NOLIBC_COMPILER_H */
diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index 5bb492555f13..d8ce91fd2e3b 100644
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -47,10 +47,7 @@ char *__nolibc_program_invocation_short_name(char *long_name)
 #endif /* NOLIBC_IGNORE_ERRNO */
 
 void _start_c(long *sp);
-__attribute__((weak,used))
-#if __nolibc_has_feature(undefined_behavior_sanitizer)
-	__attribute__((no_sanitize("function")))
-#endif
+__attribute__((weak,used)) __nolibc_no_sanitize_undefined
 void _start_c(long *sp)
 {
 	long argc;