diff --git a/test/unit/stdlib/io/file_mmap.c3 b/test/unit/stdlib/io/file_mmap.c3
index 3659ce374..665c5cc07 100644
--- a/test/unit/stdlib/io/file_mmap.c3
+++ b/test/unit/stdlib/io/file_mmap.c3
@@ -1,15 +1,13 @@
 module std::io::file @if(env::LIBC &&& env::POSIX);
-import libc;
+import std::math, libc, std::io::path;
 
 tlocal char[1024] buf;
 
 fn String random_name()
 {
-	ZString str = libc::tempnam(null, "randfile_");
-	String s = str.str_view();
-	buf[:s.len] = s[..];
-	libc::free(str);
-	return (String)buf[:s.len];
+	String filename = string::tformat("c3_test_file_%x", rand(0xFFFFFFF));
+	Path temp_dir = path::temp_directory(tmem).tappend(filename)!!;
+	return temp_dir.str_view();
 }
 
 fn void map_read_only() @test
diff --git a/test/unit/stdlib/io/file_read_write_any.c3 b/test/unit/stdlib/io/file_read_write_any.c3
index f9d155b90..f94ebc8f9 100644
--- a/test/unit/stdlib/io/file_read_write_any.c3
+++ b/test/unit/stdlib/io/file_read_write_any.c3
@@ -1,5 +1,5 @@
 module std::io::file @test;
-import std::io, libc;
+import std::io, libc, std::math;
 
 struct Data
 {
@@ -59,9 +59,10 @@ fn void read_write_any()
 
 	char[1024] buf;
 
-	ZString zname = libc::tempnam(null, "testfile_");
-	defer libc::free(zname);
-	String name = zname.str_view();
+	String filename = string::tformat("c3_test_file_%x", rand(0xFFFFFFF));
+	Path temp_dir = path::temp_directory(tmem).tappend(filename)!!;
+
+	String name = temp_dir.str_view();
     File file = file::open(name, "wb")!!;
 
 	io::write_any(&file, &data)!!;