diff --git a/ui/src/sandbox.rs b/ui/src/sandbox.rs
index 838d7a0..5fe4887 100644
--- a/ui/src/sandbox.rs
+++ b/ui/src/sandbox.rs
@@ -150,7 +150,10 @@ impl Sandbox {
             Some(file) => {
                 if CompileTarget::Hir == req.target {
                     // Run rustfmt on the generated HIR.
-                    format_command(req).arg(file)
+                    let mut rustfmt = self.format_command(req, true);
+                    rustfmt.arg(dbg!(&file));
+                    log::debug!("formatting generated HIR: {:?}", rustfmt);
+                    run_command_with_timeout(rustfmt)?;
                 }
                 read(&file)?.unwrap_or_else(String::new)
             }
@@ -200,7 +203,7 @@ impl Sandbox {
 
     pub fn format(&self, req: &FormatRequest) -> Result<FormatResponse> {
         self.write_source_code(&req.code)?;
-        let command = self.format_command(req);
+        let command = self.format_command(req, false);
 
         let output = run_command_with_timeout(command)?;
 
@@ -356,14 +359,19 @@ impl Sandbox {
         cmd
     }
 
-    fn format_command(&self, req: impl EditionRequest) -> Command {
+    fn format_command(&self, req: impl EditionRequest, single_file: bool) -> Command {
         let crate_type = CrateType::Binary;
 
         let mut cmd = self.docker_command(Some(crate_type));
 
         cmd.apply_edition(req);
 
-        cmd.arg("rustfmt").args(&["cargo", "fmt"]);
+        cmd.arg("rustfmt");
+        if single_file {
+            cmd.arg("rustfmt");
+        } else {
+            cmd.args(&["cargo", "fmt"]);
+        }
 
         log::debug!("Formatting command is {:?}", cmd);