diff --git a/usr.bin/ncal/ncal.c b/usr.bin/ncal/ncal.c
--- a/usr.bin/ncal/ncal.c
+++ b/usr.bin/ncal/ncal.c
@@ -497,6 +497,8 @@
 			monthrangeb(y, m, flag_julian_day, before, after);
 		else
 			monthranger(y, m, flag_julian_day, before, after);
+	if (ferror(stdout) != 0 || fflush(stdout) != 0)
+		err(1, "stdout");
 	return (0);
 }