diff --git a/source/gpg.zsh b/source/gpg.zsh
index 8c1a33d..fcefeb5 100644
--- a/source/gpg.zsh
+++ b/source/gpg.zsh
@@ -9,7 +9,9 @@
 # It is important that this environment variable always reflects the out‐
 # put of the tty command.
 
-GPG_TTY=$(tty)
-export GPG_TTY
+if command -v gpg-agent &> /dev/null; then
+  GPG_TTY=$(tty)
+  export GPG_TTY
+fi
 
 # vim: ft=zsh expandtab tabstop=2 shiftwidth=2