diff --git a/miri-script/src/commands.rs b/miri-script/src/commands.rs
index e4789c696b..0b3c4fb985 100644
--- a/miri-script/src/commands.rs
+++ b/miri-script/src/commands.rs
@@ -478,7 +478,11 @@ impl Command {
         // Scan for "--target" to overwrite the "MIRI_TEST_TARGET" env var so
         // that we set the MIRI_SYSROOT up the right way.
         use itertools::Itertools;
-        let target = flags.iter().tuple_windows().find(|(first, _)| first == &"--target");
+        let target = flags
+            .iter()
+            .take_while(|arg| *arg != "--")
+            .tuple_windows()
+            .find(|(first, _)| *first == "--target");
         if let Some((_, target)) = target {
             // Found it!
             e.sh.set_var("MIRI_TEST_TARGET", target);
@@ -487,6 +491,10 @@ impl Command {
             let miriflags = e.sh.var("MIRIFLAGS").unwrap_or_default();
             e.sh.set_var("MIRIFLAGS", format!("{miriflags} --target {target}"));
         }
+        // Scan for "--edition" (we'll set one ourselves if that flag is not present).
+        let have_edition =
+            flags.iter().take_while(|arg| *arg != "--").any(|arg| *arg == "--edition");
+
         // Prepare a sysroot.
         e.build_miri_sysroot(/* quiet */ true)?;
 
@@ -496,15 +504,16 @@ impl Command {
         let miri_flags = flagsplit(&miri_flags);
         let toolchain = &e.toolchain;
         let extra_flags = &e.cargo_extra_flags;
+        let edition_flags = (!have_edition).then_some("--edition=2021"); // keep in sync with `compiletest.rs`.`
         if dep {
             cmd!(
                 e.sh,
-                "cargo +{toolchain} --quiet test --test compiletest {extra_flags...} --manifest-path {miri_manifest} -- --miri-run-dep-mode {miri_flags...} {flags...}"
+                "cargo +{toolchain} --quiet test --test compiletest {extra_flags...} --manifest-path {miri_manifest} -- --miri-run-dep-mode {miri_flags...} {edition_flags...} {flags...}"
             ).quiet().run()?;
         } else {
             cmd!(
                 e.sh,
-                "cargo +{toolchain} --quiet run {extra_flags...} --manifest-path {miri_manifest} -- {miri_flags...} {flags...}"
+                "cargo +{toolchain} --quiet run {extra_flags...} --manifest-path {miri_manifest} -- {miri_flags...} {edition_flags...} {flags...}"
             ).quiet().run()?;
         }
         Ok(())
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index 91df4985c0..3394c4a49f 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -91,7 +91,7 @@ fn test_config(target: &str, path: &str, mode: Mode, with_dependencies: bool) ->
         mode,
         program,
         out_dir: PathBuf::from(std::env::var_os("CARGO_TARGET_DIR").unwrap()).join("ui"),
-        edition: Some("2021".into()),
+        edition: Some("2021".into()), // keep in sync with `./miri run`
         threads: std::env::var("MIRI_TEST_THREADS")
             .ok()
             .map(|threads| NonZeroUsize::new(threads.parse().unwrap()).unwrap()),