diff --git a/src/cli.rs b/src/cli.rs
index 11fd9c8..e43ed11 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -632,12 +632,25 @@ pub fn run_cli() -> Fido2LuksResult<()> {
             }
         },
         Command::GenerateCompletions { shell, out_dir } => {
-            Args::clap().gen_completions(
-                env!("CARGO_PKG_NAME"),
-                Shell::from_str(shell.as_str())
-                    .expect("structopt shouldn't allow us to reach this point"),
-                &out_dir,
-            );
+            // zsh won't work atm https://github.com/clap-rs/clap/issues/1822
+            if let Some(s) = shell {
+                if s.as_str() == "zsh" {
+                    unimplemented!("zsh completions are broken atm: see https://github.com/clap-rs/clap/issues/1822")
+                }
+            }
+            for variant in Shell::variants().iter().filter(|v| *v != &"zsh") {
+                if let Some(s) = shell {
+                    if *variant != s.as_str() {
+                        break;
+                    }
+                }
+                Args::clap().gen_completions(
+                    env!("CARGO_PKG_NAME"),
+                    Shell::from_str(variant)
+                        .expect("structopt shouldn't allow us to reach this point"),
+                    &out_dir,
+                );
+            }
             Ok(())
         }
     }
diff --git a/src/cli_args/mod.rs b/src/cli_args/mod.rs
index ac5744f..322e155 100644
--- a/src/cli_args/mod.rs
+++ b/src/cli_args/mod.rs
@@ -259,11 +259,12 @@ pub enum Command {
     Connected,
     Token(TokenCommand),
     /// Generate bash completion scripts
+    /// Example: fido2luks completions --shell bash /usr/share/bash-completion/completions
     #[structopt(name = "completions", setting = AppSettings::Hidden)]
     GenerateCompletions {
         /// Shell to generate completions for
-        #[structopt(possible_values = &Shell::variants()[..])]
-        shell: String,
+        #[structopt(short = "s", long = "shell",possible_values = &Shell::variants()[..])]
+        shell: Option<String>,
         out_dir: PathBuf,
     },
 }