diff --git a/include/extern/err.h b/include/extern/err.h
index ffb4f26d..f68fa29f 100644
--- a/include/extern/err.h
+++ b/include/extern/err.h
@@ -49,10 +49,10 @@ void vwarn(const char *, va_list);
 void warnx(const char *, ...);
 void vwarnx(const char *, va_list);
 
-void err(int, const char *, ...);
-void verr(int, const char *, va_list);
-void errx(int, const char *, ...);
-void verrx(int, const char *, va_list);
+_Noreturn void err(int, const char *, ...);
+_Noreturn void verr(int, const char *, va_list);
+_Noreturn void errx(int, const char *, ...);
+_Noreturn void verrx(int, const char *, va_list);
 
 #ifdef __cplusplus
 }