diff --git a/src/memory/allocator_wrapper.h b/src/memory/allocator_wrapper.h
index ebf87eb..8b066ba 100755
--- a/src/memory/allocator_wrapper.h
+++ b/src/memory/allocator_wrapper.h
@@ -61,6 +61,11 @@ public:
     allocator_wrapper(allocator_wrapper<U, AllocP> && rhs) noexcept : alloc_(std::move(rhs.alloc_)) {}
     allocator_wrapper(alloc_policy                 && rhs) noexcept : alloc_(std::move(rhs)) {}
 
+    allocator_wrapper& operator=(allocator_wrapper && rhs) noexcept {
+        alloc_ = std::move(rhs.alloc_);
+        return *this;
+    }
+
 public:
     // the other type of std_allocator
     template <typename U>