diff --git a/cli/src/complete.rs b/cli/src/complete.rs
index 56d7e87231..944b6080fb 100644
--- a/cli/src/complete.rs
+++ b/cli/src/complete.rs
@@ -55,8 +55,9 @@ fn split_help_text(line: &str) -> (&str, Option<StyledStr>) {
 }
 
 pub fn local_bookmarks() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("bookmark")
             .arg("list")
             .arg("--config-toml")
@@ -75,8 +76,9 @@ pub fn local_bookmarks() -> Vec<CompletionCandidate> {
 }
 
 pub fn tracked_bookmarks() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("bookmark")
             .arg("list")
             .arg("--tracked")
@@ -96,8 +98,9 @@ pub fn tracked_bookmarks() -> Vec<CompletionCandidate> {
 }
 
 pub fn untracked_bookmarks() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, config| {
+    with_jj(|jj, config| {
         let output = jj
+            .build()
             .arg("bookmark")
             .arg("list")
             .arg("--all-remotes")
@@ -133,8 +136,9 @@ pub fn untracked_bookmarks() -> Vec<CompletionCandidate> {
 }
 
 pub fn bookmarks() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, config| {
+    with_jj(|jj, config| {
         let output = jj
+            .build()
             .arg("bookmark")
             .arg("list")
             .arg("--all-remotes")
@@ -177,8 +181,9 @@ pub fn bookmarks() -> Vec<CompletionCandidate> {
 }
 
 pub fn git_remotes() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("git")
             .arg("remote")
             .arg("list")
@@ -211,8 +216,9 @@ pub fn aliases() -> Vec<CompletionCandidate> {
 }
 
 fn revisions(revisions: &str) -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("log")
             .arg("--no-graph")
             .arg("--limit")
@@ -244,8 +250,9 @@ pub fn all_revisions() -> Vec<CompletionCandidate> {
 }
 
 pub fn operations() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("operation")
             .arg("log")
             .arg("--no-graph")
@@ -274,8 +281,9 @@ pub fn operations() -> Vec<CompletionCandidate> {
 }
 
 pub fn workspaces() -> Vec<CompletionCandidate> {
-    with_jj(|mut jj, _| {
+    with_jj(|jj, _| {
         let output = jj
+            .build()
             .arg("--config-toml")
             .arg(r#"templates.commit_summary = 'if(description, description.first_line(), "(no description set)")'"#)
             .arg("workspace")
@@ -359,7 +367,7 @@ pub fn leaf_config_keys() -> Vec<CompletionCandidate> {
 /// In case of errors, print them and early return an empty vector.
 fn with_jj<F>(completion_fn: F) -> Vec<CompletionCandidate>
 where
-    F: FnOnce(std::process::Command, &Config) -> Result<Vec<CompletionCandidate>, CommandError>,
+    F: FnOnce(JjBuilder, &Config) -> Result<Vec<CompletionCandidate>, CommandError>,
 {
     get_jj_command()
         .and_then(|(jj, config)| completion_fn(jj, &config))
@@ -378,7 +386,7 @@ where
 /// give completion code access to custom backends. Shelling out was chosen as
 /// the preferred method, because it's more maintainable and the performance
 /// requirements of completions aren't very high.
-fn get_jj_command() -> Result<(std::process::Command, Config), CommandError> {
+fn get_jj_command() -> Result<(JjBuilder, Config), CommandError> {
     let current_exe = std::env::current_exe().map_err(user_error)?;
     let mut cmd_args = Vec::<String>::new();
 
@@ -459,10 +467,27 @@ fn get_jj_command() -> Result<(std::process::Command, Config), CommandError> {
         cmd_args.push(config_toml);
     }
 
-    let mut cmd = std::process::Command::new(current_exe);
-    cmd.args(&cmd_args);
+    let builder = JjBuilder {
+        cmd: current_exe,
+        args: cmd_args,
+    };
 
-    Ok((cmd, config))
+    Ok((builder, config))
+}
+
+/// A helper struct to allow completion functions to call jj multiple times with
+/// different arguments.
+struct JjBuilder {
+    cmd: std::path::PathBuf,
+    args: Vec<String>,
+}
+
+impl JjBuilder {
+    fn build(&self) -> std::process::Command {
+        let mut cmd = std::process::Command::new(&self.cmd);
+        cmd.args(&self.args);
+        cmd
+    }
 }
 
 #[cfg(test)]