diff --git a/include/stdex/stream.hpp b/include/stdex/stream.hpp
index b7e20b42b..cb5c81e9d 100644
--- a/include/stdex/stream.hpp
+++ b/include/stdex/stream.hpp
@@ -547,12 +547,8 @@ namespace stdex
 			///
 			size_t write_sa(_In_ LPSAFEARRAY sa)
 			{
-				long ubound, lbound;
-				if (FAILED(SafeArrayGetUBound(sa, 1, &ubound)) ||
-					FAILED(SafeArrayGetLBound(sa, 1, &lbound)))
-					throw std::invalid_argument("SafeArrayGet[UL]Bound failed");
-				safearray_accessor<void> a(sa);
-				return write(a.data(), static_cast<size_t>(ubound) - lbound + 1);
+				safearray_accessor_with_size<uint8_t> a(sa);
+				return write(a.data(), a.size());
 			}
 #endif
 
diff --git a/include/stdex/system.hpp b/include/stdex/system.hpp
index 11cfc3db7..737a8fcff 100644
--- a/include/stdex/system.hpp
+++ b/include/stdex/system.hpp
@@ -231,6 +231,32 @@ namespace stdex
 		T* m_data;
 	};
 
+	template <class T>
+	class safearray_accessor_with_size : public safearray_accessor<T>
+	{
+	public:
+		safearray_accessor_with_size(_In_ LPSAFEARRAY sa) : safearray_accessor<T>(sa)
+		{
+			m_size = SafeArrayGetElemsize(sa);
+			for (UINT d = 1, dim = SafeArrayGetDim(sa); d <= dim; ++d) {
+				long ubound, lbound;
+				if (FAILED(SafeArrayGetUBound(sa, d, &ubound)) ||
+					FAILED(SafeArrayGetLBound(sa, d, &lbound)))
+					throw std::invalid_argument("SafeArrayGet[UL]Bound failed");
+				m_size *= static_cast<size_t>(ubound) - lbound + 1;
+			}
+			m_size /= sizeof(T);
+		}
+
+		///
+		/// Return size in number of elements
+		///
+		size_t size() const { return m_size; }
+
+	protected:
+		size_t m_size;
+	};
+
 	///
 	/// Deleter for unique_ptr using SafeArrayDestroy
 	///