autoenv.zsh | 3 +++

diff --git a/autoenv.zsh b/autoenv.zsh
index 0cc056684187d932f39ddd42729fe2ce13d647f4..b8a8f056170dcbf99d0b5581245fb8cface1e031 100644
--- a/autoenv.zsh
+++ b/autoenv.zsh
@@ -152,6 +152,9 @@   _autoenv_deauthorize $env_file
   _autoenv_hash_pair $env_file >> $AUTOENV_ENV_FILENAME
 }
 
+# Deauthorize a given filename, by removing it from the auth file.
+# This uses `test -s` to only handle non-empty files, and a subshell to
+# allow for writing to the same file again.
 _autoenv_deauthorize() {
   local env_file=${1:A}
   if [[ -s $AUTOENV_ENV_FILENAME ]]; then