diff --git a/src/tools/run-make-support/src/lib.rs b/src/tools/run-make-support/src/lib.rs
index 674860f8413b6..dd1f306dd6167 100644
--- a/src/tools/run-make-support/src/lib.rs
+++ b/src/tools/run-make-support/src/lib.rs
@@ -1,7 +1,7 @@
 use std::env;
+use std::ffi::OsStr;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Output};
-
 pub use wasmparser;
 
 pub fn out_dir() -> PathBuf {
@@ -43,7 +43,7 @@ impl RustcInvocationBuilder {
         Self { cmd }
     }
 
-    pub fn arg(&mut self, arg: &str) -> &mut RustcInvocationBuilder {
+    pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut RustcInvocationBuilder {
         self.cmd.arg(arg);
         self
     }
diff --git a/tests/run-make/hir-tree/Makefile b/tests/run-make/hir-tree/Makefile
deleted file mode 100644
index b0450ea4bc5fd..0000000000000
--- a/tests/run-make/hir-tree/Makefile
+++ /dev/null
@@ -1,8 +0,0 @@
-include ../tools.mk
-
-# Test that hir-tree output doesn't crash and includes
-# the string constant we would expect to see.
-
-all:
-	$(RUSTC) -o $(TMPDIR)/input.hir -Z unpretty=hir-tree input.rs
-	$(CGREP) '"Hello, Rustaceans!\n"' < $(TMPDIR)/input.hir
diff --git a/tests/run-make/hir-tree/rmake.rs b/tests/run-make/hir-tree/rmake.rs
new file mode 100644
index 0000000000000..799dfcee564de
--- /dev/null
+++ b/tests/run-make/hir-tree/rmake.rs
@@ -0,0 +1,17 @@
+extern crate run_make_support;
+
+use run_make_support::{out_dir, rustc};
+
+// Test that hir-tree output doesn't crash and includes
+// the string constant we would expect to see.
+
+fn main() {
+    rustc()
+        .arg("-o")
+        .arg(&out_dir().join("input.hir"))
+        .arg("-Zunpretty=hir-tree")
+        .arg("input.rs")
+        .run();
+    let file = std::fs::read_to_string(&out_dir().join("input.hir")).unwrap();
+    assert!(file.contains(r#""Hello, Rustaceans!\n""#));
+}