diff --git a/lib/roken/err.h b/lib/roken/err.h
index bb7057910..473b42071 100644
--- a/lib/roken/err.h
+++ b/lib/roken/err.h
@@ -11,12 +11,12 @@
 
 extern char *__progname;
 
-void warnerr(int doexit, int eval, int doerrno, const char *fmt, va_list ap);
-
 #ifndef __GNUC__
 #define __attribute__(x)
 #endif
 
+void warnerr(int doexit, int eval, int doerrno, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 4, 0)));
+
 void verr(int eval, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 2, 0)));
 void err(int eval, const char *fmt, ...)  __attribute__ ((noreturn, format (printf, 2, 3)));
 void verrx(int eval, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 2, 0)));
diff --git a/lib/roken/err.hin b/lib/roken/err.hin
index bb7057910..473b42071 100644
--- a/lib/roken/err.hin
+++ b/lib/roken/err.hin
@@ -11,12 +11,12 @@
 
 extern char *__progname;
 
-void warnerr(int doexit, int eval, int doerrno, const char *fmt, va_list ap);
-
 #ifndef __GNUC__
 #define __attribute__(x)
 #endif
 
+void warnerr(int doexit, int eval, int doerrno, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 4, 0)));
+
 void verr(int eval, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 2, 0)));
 void err(int eval, const char *fmt, ...)  __attribute__ ((noreturn, format (printf, 2, 3)));
 void verrx(int eval, const char *fmt, va_list ap) __attribute__ ((noreturn, format (printf, 2, 0)));