diff --git a/t/README b/t/README
index b3f7b449c3..1a1361a806 100644
--- a/t/README
+++ b/t/README
@@ -655,7 +655,7 @@ library for your script to use.
 		test_expect_code 1 git merge "merge msg" B master
 	'
 
- - test_must_fail <git-command>
+ - test_must_fail [<options>] <git-command>
 
    Run a git command and ensure it fails in a controlled way.  Use
    this instead of "! <git-command>".  When git-command dies due to a
@@ -663,11 +663,21 @@ library for your script to use.
    treats it as just another expected failure, which would let such a
    bug go unnoticed.
 
- - test_might_fail <git-command>
+   Accepts the following options:
+
+     ok=<signal-name>[,<...>]:
+       Don't treat an exit caused by the given signal as error.
+       Multiple signals can be specified as a comma separated list.
+       Currently recognized signal names are: sigpipe, success.
+       (Don't use 'success', use 'test_might_fail' instead.)
+
+ - test_might_fail [<options>] <git-command>
 
    Similar to test_must_fail, but tolerate success, too.  Use this
    instead of "<git-command> || :" to catch failures due to segv.
 
+   Accepts the same options as test_must_fail.
+
  - test_cmp <expected> <actual>
 
    Check whether the content of the <actual> file matches the
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 67b5994afb..8a8a9329ee 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -610,6 +610,14 @@ list_contains () {
 #
 # Writing this as "! git checkout ../outerspace" is wrong, because
 # the failure could be due to a segv.  We want a controlled failure.
+#
+# Accepts the following options:
+#
+#   ok=<signal-name>[,<...>]:
+#     Don't treat an exit caused by the given signal as error.
+#     Multiple signals can be specified as a comma separated list.
+#     Currently recognized signal names are: sigpipe, success.
+#     (Don't use 'success', use 'test_might_fail' instead.)
 
 test_must_fail () {
 	case "$1" in
@@ -656,6 +664,8 @@ test_must_fail () {
 #
 # Writing "git config --unset all.configuration || :" would be wrong,
 # because we want to notice if it fails due to segv.
+#
+# Accepts the same options as test_must_fail.
 
 test_might_fail () {
 	test_must_fail ok=success "$@"