diff --git a/src/block/block.h b/src/block/block.h
index 74e568f..be046d8 100644
--- a/src/block/block.h
+++ b/src/block/block.h
@@ -18,8 +18,10 @@ namespace MultiArrayHelper
     class BlockBinaryOp
     {
     public:
-	BlockBinaryOp() = default;
-	BlockResult<T> operator()(const BlockClass1& arg1, const BlockClass2& arg2);
+	BlockBinaryOp(BlockResult<T>& mRes);
+	void operator()(const BlockClass1& arg1, const BlockClass2& arg2);
+    private:
+	BlockResult<T>& mRes;
     };
 
     template <typename T, class OpFunc, class BlockClass>
@@ -179,18 +181,18 @@ namespace MultiArrayHelper
      *********************/
 
     template <typename T, class OpFunc, class BlockClass1, class BlockClass2>
-    BlockResult<T>
-    BlockBinaryOp<T,OpFunc,BlockClass1,BlockClass2>::operator()(const BlockClass1& arg1,
-								const BlockClass2& arg2)
+    BlockBinaryOp<T,OpFunc,BlockClass1,BlockClass2>::BlockBinaryOp(BlockResult<T>& res) : mRes(res) {}
+    
+    template <typename T, class OpFunc, class BlockClass1, class BlockClass2>
+    void BlockBinaryOp<T,OpFunc,BlockClass1,BlockClass2>::operator()(const BlockClass1& arg1,
+								     const BlockClass2& arg2)
     {
 	static OpFunc f;
-	BlockResult<T> res(arg1.size());
-	assert(res.init() and arg1.init() and arg2.init());
+	assert(mRes.init() and arg1.init() and arg2.init());
 	assert(arg1.size() == arg2.size());
 	for(size_t i = 0; i != arg1.size(); ++i){
-	    res[i] = f(arg1[i], arg2[i]);
+	    mRes[i] = f(arg1[i], arg2[i]);
 	}
-	return res;
     }
 
     template <typename T, class OpFunc, class BlockClass>
diff --git a/src/multi_array_operation.h b/src/multi_array_operation.h
index 4dce8f6..bf30109 100644
--- a/src/multi_array_operation.h
+++ b/src/multi_array_operation.h
@@ -472,7 +472,7 @@ namespace MultiArrayTools
     template <typename T, class OpFunction, class... Ops>
     const BlockResult<T>& Operation<T,OpFunction,Ops...>::get() const
     {
-	mRes = std::move( PackNum<sizeof...(Ops)-1>::template unpackArgs<T,OpFunction>(mOps) );
+	PackNum<sizeof...(Ops)-1>::template unpackArgs<T,OpFunction>(mRes, mOps);
 	return mRes;
     }
 
diff --git a/src/pack_num.h b/src/pack_num.h
index d6978cf..0a3e677 100644
--- a/src/pack_num.h
+++ b/src/pack_num.h
@@ -28,9 +28,9 @@ namespace MultiArrayHelper
 	}
 
 	template <typename T, class Func, class ArgTuple, class... Args>
-	static BlockResult<T> unpackArgs(const ArgTuple& tp, const Args&... args)
+	static void unpackArgs(BlockResult<T>& res, const ArgTuple& tp, const Args&... args)
 	{
-	    return PackNum<N-1>::template unpackArgs<T,Func>(tp, std::get<N>(tp).get(), args...);
+	    PackNum<N-1>::template unpackArgs<T,Func>(res, tp, std::get<N>(tp).get(), args...);
 	}
 
 	template <typename... T>
@@ -46,12 +46,12 @@ namespace MultiArrayHelper
     {
 
 	template <typename T, class Func, class ArgTuple, class... Args>
-	static BlockResult<T> unpackArgs(const ArgTuple& tp, const Args&... args)
+	static void unpackArgs(BlockResult<T>& res, const ArgTuple& tp, const Args&... args)
 	{
 	    static_assert(sizeof...(Args) == std::tuple_size<ArgTuple>::value-1,
 			  "inconsistent number of arguments");
-	    static BlockBinaryOp<T,Func,decltype(std::get<0>(tp).get()), decltype(args)...> f;
-	    return f(std::get<0>(tp).get(), args...);
+	    BlockBinaryOp<T,Func,decltype(std::get<0>(tp).get()), decltype(args)...> f(res);
+	    f(std::get<0>(tp).get(), args...);
 	}
 	
 	template <class... Ops>