diff --git a/include/chaiscript/language/chaiscript_eval.hpp b/include/chaiscript/language/chaiscript_eval.hpp
index 5679ac1d..104e174d 100644
--- a/include/chaiscript/language/chaiscript_eval.hpp
+++ b/include/chaiscript/language/chaiscript_eval.hpp
@@ -473,7 +473,11 @@ namespace chaiscript {
           }
         } else if (this->text == ":=") {
           if (params[0].is_undef() || Boxed_Value::type_match(params[0], params[1])) {
-            params[0].assign(params[1]);
+            if (params[1].get_type_info().is_arithmetic() && params[0].get_type_info().is_arithmetic()) {
+              params[0].assign(Boxed_Number::clone(params[1]));
+            } else {
+              params[0].assign(params[1]);
+            }
             params[0].reset_return_value();
           } else {
             throw exception::eval_error("Mismatched types in equation");
diff --git a/include/chaiscript/language/chaiscript_optimizer.hpp b/include/chaiscript/language/chaiscript_optimizer.hpp
index e8048eb3..b35dd31b 100644
--- a/include/chaiscript/language/chaiscript_optimizer.hpp
+++ b/include/chaiscript/language/chaiscript_optimizer.hpp
@@ -397,8 +397,9 @@ namespace chaiscript {
                                         assert(children.size() == 1);
                                         chaiscript::eval::detail::Scope_Push_Pop spp(t_ss);
 
-                                        int i = start_int;
-                                        t_ss.add_object(id, var(&i));
+                                        Boxed_Value bv_i(start_int);
+                                        auto &i = *static_cast<int *>(bv_i.get_ptr());
+                                        t_ss.add_object(id, bv_i);
 
                                         try {
                                           for (; i < end_int; ++i) {
diff --git a/unittests/assign_no_aliasing.chai b/unittests/assign_no_aliasing.chai
new file mode 100644
index 00000000..554b0e84
--- /dev/null
+++ b/unittests/assign_no_aliasing.chai
@@ -0,0 +1,7 @@
+// Verify that := performs a value copy, not an alias
+var a = 10
+var b = 20
+a := b
+++b
+assert_equal(20, a)
+assert_equal(21, b)
diff --git a/unittests/async_return_value.chai b/unittests/async_return_value.chai
new file mode 100644
index 00000000..144b8b4a
--- /dev/null
+++ b/unittests/async_return_value.chai
@@ -0,0 +1,13 @@
+var func = fun(){
+  var ret = 0;
+  for (var i = 0; i < 1000; ++i) {
+    ret := i;
+  }
+  return ret;
+}
+
+var&fut1 = async(func);
+var fut2 = async(func);
+
+assert_equal(999, fut1.get())
+assert_equal(999, fut2.get())