diff --git a/completions/zsh/_f00bar b/completions/zsh/_f00bar
index 9529a01..a8f5494 100644
--- a/completions/zsh/_f00bar
+++ b/completions/zsh/_f00bar
@@ -4,6 +4,6 @@ _arguments \
     -s \
     '(-v --version)'{-v,--version}'[show the version number and quit]' \
     '(-h --help)'{-h,--help}'[show help message and quit]' \
-    '(-b --backend)'{-b,--backend}'[backend to use; xcb,wayland,auto (default: auto)]' \
-    '(-c --config)'{-c,--config}'[alternative configuration file]' \
+    '(-b --backend)'{-b,--backend}'[backend to use (default: auto)]:backend:(xcb wayland auto)' \
+    '(-c --config)'{-c,--config}'[alternative configuration file]:filename:_files' \
     '(-C --validate)'{-C,--validate}'[verify configuration then quit]'