diff --git a/js/src/builtin/Array.js b/js/src/builtin/Array.js
index d020fbaa9fa..62179cbec94 100644
--- a/js/src/builtin/Array.js
+++ b/js/src/builtin/Array.js
@@ -817,7 +817,7 @@ function ArrayReducePar(func, mode) {
     var numSlices = slicesInfo.count;
     var subreductions = NewDenseArray(numSlices);
 
-    ForkJoin(reduceThread, 0, numSlices, ForkJoinMode(mode), null);
+    ForkJoin(reduceThread, 0, numSlices, ForkJoinMode(mode), subreductions);
 
     var accumulator = subreductions[0];
     for (var i = 1; i < numSlices; i++)
diff --git a/js/src/jit-test/tests/parallel/bug1033115-2.js b/js/src/jit-test/tests/parallel/bug1033115-2.js
new file mode 100644
index 00000000000..fb02a2f5cbf
--- /dev/null
+++ b/js/src/jit-test/tests/parallel/bug1033115-2.js
@@ -0,0 +1,21 @@
+// Failed to pass the subreductions as an assignment root to Array.prototype.reducePar,
+// fuzzing test case discovered separately.
+
+if (!getBuildConfiguration().parallelJS)
+  quit(0);
+
+x = [];
+y = x.mapPar(function() {});
+Object.defineProperty(y, 3, {
+    get: (function( ... $8)  {
+        try {
+            Int8Array(y);
+            x.reducePar(function() function q() 1);
+        } catch (e) {}
+    })
+});
+var x = [1,2,3];
+function rsh() { 
+ return y.toSource() >> 2.0; 
+}
+rsh();
diff --git a/js/src/jit-test/tests/parallel/bug1033115.js b/js/src/jit-test/tests/parallel/bug1033115.js
new file mode 100644
index 00000000000..2a9f76f637a
--- /dev/null
+++ b/js/src/jit-test/tests/parallel/bug1033115.js
@@ -0,0 +1,13 @@
+// Failed to pass the subreductions as an assignment root to Array.prototype.reducePar,
+// fuzzing test case.
+
+if (!getBuildConfiguration().parallelJS)
+  quit(0);
+
+x = []
+x[8] = ((function() {})());
+for each(let a in [0, 0]) {
+    x.reducePar(function() {
+        return [0];
+    });
+}