diff --git a/src/test/run-pass/realloc-16687.rs b/src/test/run-pass/realloc-16687.rs
new file mode 100644
index 00000000000..2e8c23fe5ba
--- /dev/null
+++ b/src/test/run-pass/realloc-16687.rs
@@ -0,0 +1,167 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// alloc::heap::reallocate test.
+//
+// Ideally this would be revised to use no_std, but for now it serves
+// well enough to reproduce (and illustrate) the bug from #16687.
+
+extern crate alloc;
+
+use alloc::heap;
+use std::ptr;
+
+fn main() {
+    unsafe {
+        assert!(test_triangle());
+    }
+}
+
+unsafe fn test_triangle() -> bool {
+    static COUNT : uint = 16;
+    let mut ascend = Vec::from_elem(COUNT, ptr::mut_null());
+    let ascend = ascend.as_mut_slice();
+    static ALIGN : uint = 1;
+
+    // Checks that `ascend` forms triangle of acending size formed
+    // from pairs of rows (where each pair of rows is equally sized),
+    // and the elements of the triangle match their row-pair index.
+    unsafe fn sanity_check(ascend: &[*mut u8]) {
+        for i in range(0u, COUNT / 2) {
+            let (p0, p1, size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+            for j in range(0u, size) {
+                assert_eq!(*p0.offset(j as int), i as u8);
+                assert_eq!(*p1.offset(j as int), i as u8);
+            }
+        }
+    }
+
+    static PRINT : bool = false;
+
+    unsafe fn allocate(size: uint, align: uint) -> *mut u8 {
+        if PRINT { println!("allocate(size={:u} align={:u})", size, align); }
+
+        let ret = heap::allocate(size, align);
+
+        if PRINT { println!("allocate(size={:u} align={:u}) ret: 0x{:010x}",
+                            size, align, ret as uint);
+        }
+
+        ret
+    }
+    unsafe fn reallocate(ptr: *mut u8, size: uint, align: uint,
+                             old_size: uint) -> *mut u8 {
+        if PRINT {
+            println!("reallocate(ptr=0x{:010x} size={:u} align={:u} old_size={:u})",
+                     ptr as uint, size, align, old_size);
+        }
+
+        let ret = heap::reallocate(ptr, size, align, old_size);
+
+        if PRINT {
+            println!("reallocate(ptr=0x{:010x} size={:u} align={:u} old_size={:u}) \
+                      ret: 0x{:010x}",
+                     ptr as uint, size, align, old_size, ret as uint);
+        }
+        ret
+    }
+
+    fn idx_to_size(i: uint) -> uint { (i+1) * 10 }
+
+    // Allocate pairs of rows that form a triangle shape.  (Hope is
+    // that at least two rows will be allocated near each other, so
+    // that we trigger the bug (a buffer overrun) in an observable
+    // way.)
+    for i in range(0u, COUNT / 2) {
+        let size = idx_to_size(i);
+        ascend[2*i]   = allocate(size, ALIGN);
+        ascend[2*i+1] = allocate(size, ALIGN);
+    }
+
+    // Initialize each pair of rows to distinct value.
+    for i in range(0u, COUNT / 2) {
+        let (p0, p1, size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+        for j in range(0, size) {
+            *p0.offset(j as int) = i as u8;
+            *p1.offset(j as int) = i as u8;
+        }
+    }
+
+    sanity_check(ascend.as_slice());
+    test_1(ascend);
+    test_2(ascend);
+    test_3(ascend);
+    test_4(ascend);
+
+    return true;
+
+    // Test 1: turn the triangle into a square (in terms of
+    // allocation; initialized portion remains a triangle) by
+    // realloc'ing each row from top to bottom, and checking all the
+    // rows as we go.
+    unsafe fn test_1(ascend: &mut [*mut u8]) {
+        let new_size = idx_to_size(COUNT-1);
+        for i in range(0u, COUNT / 2) {
+            let (p0, p1, old_size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+            assert!(old_size < new_size);
+
+            ascend[2*i] = reallocate(p0, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+
+            ascend[2*i+1] = reallocate(p1, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+        }
+    }
+
+    // Test 2: turn the square back into a triangle, top to bottom.
+    unsafe fn test_2(ascend: &mut [*mut u8]) {
+        let old_size = idx_to_size(COUNT-1);
+        for i in range(0u, COUNT / 2) {
+            let (p0, p1, new_size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+            assert!(new_size < old_size);
+
+            ascend[2*i] = reallocate(p0, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+
+            ascend[2*i+1] = reallocate(p1, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+        }
+    }
+
+    // Test 3: turn triangle into a square, bottom to top.
+    unsafe fn test_3(ascend: &mut [*mut u8]) {
+        let new_size = idx_to_size(COUNT-1);
+        for i in range(0u, COUNT / 2).rev() {
+            let (p0, p1, old_size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+            assert!(old_size < new_size);
+
+            ascend[2*i+1] = reallocate(p1, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+
+            ascend[2*i] = reallocate(p0, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+        }
+    }
+
+    // Test 4: turn the square back into a triangle, bottom to top.
+    unsafe fn test_4(ascend: &mut [*mut u8]) {
+        let old_size = idx_to_size(COUNT-1);
+        for i in range(0u, COUNT / 2).rev() {
+            let (p0, p1, new_size) = (ascend[2*i], ascend[2*i+1], idx_to_size(i));
+            assert!(new_size < old_size);
+
+            ascend[2*i+1] = reallocate(p1, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+
+            ascend[2*i] = reallocate(p0, new_size, ALIGN, old_size);
+            sanity_check(ascend.as_slice());
+        }
+    }
+}