diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 891719a..f0e1ee5 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1003,6 +1003,7 @@
 	assert_true()		assert that an expression is true
 	assert_exception()	assert that a command throws an exception
 	assert_beeps()		assert that a command beeps
+	assert_nobeep()		assert that a command does not cause a beep
 	assert_fails()		assert that a command fails
 	assert_report()		report a test failure
 	test_alloc_fail()	make memory allocation fail