diff --git a/gnupg2.sh b/gnupg2.sh
index 485ab8b..fce8fc6 100644
--- a/gnupg2.sh
+++ b/gnupg2.sh
@@ -1,3 +1,3 @@
-if [[ $- == *i* ]]; then
-    export GPG_TTY=$(tty)
-fi
+case "$-" in *i*)
+    export GPG_TTY=$(tty) ;;
+esac