diff --git a/Documentation/git-clean.txt b/Documentation/git-clean.txt
index 94b6d19..641681f 100644
--- a/Documentation/git-clean.txt
+++ b/Documentation/git-clean.txt
@@ -34,8 +34,12 @@
 -f::
 --force::
 	If the Git configuration variable clean.requireForce is not set
-	to false, 'git clean' will refuse to run unless given -f, -n or
-	-i.
+	to false, 'git clean' will refuse to delete files or directories
+	unless given -f, -n or -i. Git will refuse to delete directories
+	with .git sub directory or file unless a second -f
+	is given. This affects also git submodules where the storage area
+	of the removed submodule under .git/modules/ is not removed until
+	-f is given twice.
 
 -i::
 --interactive::