diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index a0ef798201e..5212f1430d8 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -3785,10 +3785,13 @@ fn run_rmake_v2_test(&self) {
         debug!(?support_lib_deps);
         debug!(?support_lib_deps_deps);
 
-        let mut host_dylib_env_paths = String::new();
-        host_dylib_env_paths.push_str(&cwd.join(&self.config.compile_lib_path).to_string_lossy());
-        host_dylib_env_paths.push(':');
-        host_dylib_env_paths.push_str(&env::var(dylib_env_var()).unwrap());
+        let orig_dylib_env_paths =
+            Vec::from_iter(env::split_paths(&env::var(dylib_env_var()).unwrap()));
+
+        let mut host_dylib_env_paths = Vec::new();
+        host_dylib_env_paths.push(cwd.join(&self.config.compile_lib_path));
+        host_dylib_env_paths.extend(orig_dylib_env_paths.iter().cloned());
+        let host_dylib_env_paths = env::join_paths(host_dylib_env_paths).unwrap();
 
         let mut cmd = Command::new(&self.config.rustc_path);
         cmd.arg("-o")
@@ -3834,19 +3837,15 @@ fn run_rmake_v2_test(&self) {
         // Finally, we need to run the recipe binary to build and run the actual tests.
         debug!(?recipe_bin);
 
-        let mut dylib_env_paths = String::new();
-        dylib_env_paths.push_str(&env::var(dylib_env_var()).unwrap());
-        dylib_env_paths.push(':');
-        dylib_env_paths.push_str(&support_lib_path.parent().unwrap().to_string_lossy());
-        dylib_env_paths.push(':');
-        dylib_env_paths.push_str(
-            &stage_std_path.join("rustlib").join(&self.config.host).join("lib").to_string_lossy(),
-        );
+        let mut dylib_env_paths = orig_dylib_env_paths.clone();
+        dylib_env_paths.push(support_lib_path.parent().unwrap().to_path_buf());
+        dylib_env_paths.push(stage_std_path.join("rustlib").join(&self.config.host).join("lib"));
+        let dylib_env_paths = env::join_paths(dylib_env_paths).unwrap();
 
-        let mut target_rpath_env_path = String::new();
-        target_rpath_env_path.push_str(&tmpdir.to_string_lossy());
-        target_rpath_env_path.push(':');
-        target_rpath_env_path.push_str(&dylib_env_paths);
+        let mut target_rpath_env_path = Vec::new();
+        target_rpath_env_path.push(&tmpdir);
+        target_rpath_env_path.extend(&orig_dylib_env_paths);
+        let target_rpath_env_path = env::join_paths(target_rpath_env_path).unwrap();
 
         let mut cmd = Command::new(&recipe_bin);
         cmd.current_dir(&self.testpaths.file)