diff --git a/cargo-miri/src/phases.rs b/cargo-miri/src/phases.rs
index dba3000a80..81ff68545c 100644
--- a/cargo-miri/src/phases.rs
+++ b/cargo-miri/src/phases.rs
@@ -364,7 +364,7 @@ pub fn phase_rustc(mut args: impl Iterator<Item = String>, phase: RustcPhase) {
             let out_filename = out_filename.expect("rustdoc must pass `-o`");
 
             cmd.args(&args);
-            cmd.env("MIRI_BE_RUSTC", "rustdoc");
+            cmd.env("MIRI_BE_RUSTC", "target");
 
             if verbose > 0 {
                 eprintln!(
diff --git a/src/bin/miri.rs b/src/bin/miri.rs
index 581e129c9e..8028803dde 100644
--- a/src/bin/miri.rs
+++ b/src/bin/miri.rs
@@ -123,31 +123,14 @@ impl rustc_driver::Callbacks for MiriCompilerCalls {
     }
 }
 
-#[derive(Copy, Clone, Debug, PartialEq)]
-enum MiriBeRustcMode {
-    Target,
-    Host,
-    Rustdoc,
-}
-
-impl MiriBeRustcMode {
-    fn target_crate(self) -> bool {
-        use MiriBeRustcMode::*;
-        match self {
-            Target | Rustdoc => true,
-            Host => false,
-        }
-    }
-}
-
 struct MiriBeRustCompilerCalls {
-    mode: MiriBeRustcMode,
+    target_crate: bool,
 }
 
 impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
     #[allow(rustc::potential_query_instability)] // rustc_codegen_ssa (where this code is copied from) also allows this lint
     fn config(&mut self, config: &mut Config) {
-        if config.opts.prints.is_empty() && self.mode == MiriBeRustcMode::Target {
+        if config.opts.prints.is_empty() && self.target_crate {
             // Queries overridden here affect the data stored in `rmeta` files of dependencies,
             // which will be used later in non-`MIRI_BE_RUSTC` mode.
             config.override_queries = Some(|_, local_providers| {
@@ -203,11 +186,9 @@ impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
         queries: &'tcx rustc_interface::Queries<'tcx>,
     ) -> Compilation {
         queries.global_ctxt().unwrap().enter(|tcx| {
-            // Make sure compile_fail tests with post-monomorphization const-eval errors work as
-            // intended in rustdoc mode.
-            if self.mode == MiriBeRustcMode::Rustdoc {
-                let _ = tcx.collect_and_partition_mono_items(());
-            }
+            // We are emulating regular rustc builds, which would perform post-mono const-eval.
+            // So let's also do that here, even if we might be running with `--emit=metadata`.
+            let _ = tcx.collect_and_partition_mono_items(());
         });
         Compilation::Continue
     }
@@ -383,18 +364,19 @@ fn main() {
             rustc_driver::install_ice_hook(rustc_driver::DEFAULT_BUG_REPORT_URL, |_| ());
         rustc_driver::init_rustc_env_logger(&early_dcx);
 
-        let mode = match crate_kind.to_str().unwrap_or_default() {
-            "target" => MiriBeRustcMode::Target,
-            "rustdoc" => MiriBeRustcMode::Rustdoc,
-            "host" => MiriBeRustcMode::Host,
-            _ => panic!("invalid `MIRI_BE_RUSTC` value: {crate_kind:?}"),
+        let target_crate = if crate_kind == "target" {
+            true
+        } else if crate_kind == "host" {
+            false
+        } else {
+            panic!("invalid `MIRI_BE_RUSTC` value: {crate_kind:?}")
         };
 
         // We cannot use `rustc_driver::main` as we need to adjust the CLI arguments.
         run_compiler(
             args,
-            mode.target_crate(),
-            &mut MiriBeRustCompilerCalls { mode },
+            target_crate,
+            &mut MiriBeRustCompilerCalls { target_crate },
             using_internal_features,
         )
     }