diff --git a/src/test/run-pass/vector-sort-failure-safe.rs b/src/test/run-pass/vector-sort-failure-safe.rs
index a8ab0e48ccf8a..46f760722a605 100644
--- a/src/test/run-pass/vector-sort-failure-safe.rs
+++ b/src/test/run-pass/vector-sort-failure-safe.rs
@@ -9,41 +9,56 @@
 // except according to those terms.
 
 use std::task;
-use std::rand::{task_rng, Rng};
+use std::sync::atomics::{AtomicUint, INIT_ATOMIC_UINT, Relaxed};
+use std::rand::{task_rng, Rng, Rand};
 
-const MAX_LEN: uint = 20;
-static mut drop_counts: [uint, .. MAX_LEN] = [0, .. MAX_LEN];
-static mut clone_count: uint = 0;
+const REPEATS: uint = 5;
+const MAX_LEN: uint = 32;
+static drop_counts: [AtomicUint, .. MAX_LEN] =
+    // FIXME #5244: AtomicUint is not Copy.
+    [
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
 
-#[deriving(Rand, PartialEq, PartialOrd, Eq, Ord)]
-struct DropCounter { x: uint, clone_num: uint }
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+        INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT, INIT_ATOMIC_UINT,
+     ];
 
-impl Clone for DropCounter {
-    fn clone(&self) -> DropCounter {
-        let num = unsafe { clone_count };
-        unsafe { clone_count += 1; }
+static creation_count: AtomicUint = INIT_ATOMIC_UINT;
+
+#[deriving(Clone, PartialEq, PartialOrd, Eq, Ord)]
+struct DropCounter { x: uint, creation_id: uint }
+
+impl Rand for DropCounter {
+    fn rand<R: Rng>(rng: &mut R) -> DropCounter {
+        // (we're not using this concurrently, so Relaxed is fine.)
+        let num = creation_count.fetch_add(1, Relaxed);
         DropCounter {
-            x: self.x,
-            clone_num: num
+            x: rng.gen(),
+            creation_id: num
         }
     }
 }
 
 impl Drop for DropCounter {
     fn drop(&mut self) {
-        unsafe {
-            // Rand creates some with arbitrary clone_nums
-            if self.clone_num < MAX_LEN {
-                drop_counts[self.clone_num] += 1;
-            }
-        }
+        drop_counts[self.creation_id].fetch_add(1, Relaxed);
     }
 }
 
 pub fn main() {
+    assert!(MAX_LEN <= std::uint::BITS);
     // len can't go above 64.
-    for len in range(2u, MAX_LEN) {
-        for _ in range(0i, 10) {
+    for len in range(2, MAX_LEN) {
+        for _ in range(0, REPEATS) {
+            // reset the count for these new DropCounters, so their
+            // IDs start from 0.
+            creation_count.store(0, Relaxed);
+
             let main = task_rng().gen_iter::<DropCounter>()
                                  .take(len)
                                  .collect::<Vec<DropCounter>>();
@@ -56,14 +71,13 @@ pub fn main() {
             // ... and then fail on each and every single one.
             for fail_countdown in range(0i, count) {
                 // refresh the counters.
-                unsafe {
-                    drop_counts = [0, .. MAX_LEN];
-                    clone_count = 0;
+                for c in drop_counts.iter() {
+                    c.store(0, Relaxed);
                 }
 
                 let v = main.clone();
 
-                task::try(proc() {
+                let _ = task::try(proc() {
                         let mut v = v;
                         let mut fail_countdown = fail_countdown;
                         v.as_mut_slice().sort_by(|a, b| {
@@ -77,13 +91,11 @@ pub fn main() {
 
                 // check that the number of things dropped is exactly
                 // what we expect (i.e. the contents of `v`).
-                unsafe {
-                    for (i, &c) in drop_counts.iter().enumerate() {
-                        let expected = if i < len {1} else {0};
-                        assert!(c == expected,
-                                "found drop count == {} for i == {}, len == {}",
-                                c, i, len);
-                    }
+                for (i, c) in drop_counts.iter().enumerate().take(len) {
+                    let count = c.load(Relaxed);
+                    assert!(count == 1,
+                            "found drop count == {} for i == {}, len == {}",
+                            count, i, len);
                 }
             }
         }