diff --git a/protocol/esta/rdm/message.cpp b/protocol/esta/rdm/message.cpp
index e128a41..37b04bc 100644
--- a/protocol/esta/rdm/message.cpp
+++ b/protocol/esta/rdm/message.cpp
@@ -233,8 +233,8 @@ void Message::writeDiscBranch(std::vector<uint8_t> &data) const
   data.push_back(0xaa);       //!< Preamble separator byte
 
   uint16_t sum = 0;
-  for ( const uint8_t& v : data_)
-    sum = addSum_(sum, v);
+  for (const auto &v : data_)
+    addSum_(sum, v);
 
   std::vector<uint8_t> d = data_;
   writeType<uint16_t>(d, sum);
@@ -288,22 +288,22 @@ uint16_t Message::checksum() const
 {
   uint16_t sum = 0;
 
-  sum = addSum_(sum, SC_RDM);
-  sum = addSum_(sum, SC_SUB_MESSAGE);
-  sum = addSum_(sum, 24 + length());
-  sum = addSum_(sum, source.manufacturer);
-  sum = addSum_(sum, source.device);
-  sum = addSum_(sum, destination.manufacturer);
-  sum = addSum_(sum, destination.device);
-  sum = addSum_(sum, transaction);
-  sum = addSum_(sum, portID);
-  sum = addSum_(sum, messageCount);
-  sum = addSum_(sum, subDevice);
-  sum = addSum_(sum, commandClass);
-  sum = addSum_(sum, parameterId);
-  sum = addSum_(sum, length());
-  for (uint8_t val : data_)
-    sum = addSum_(sum, val);
+  addSum_(sum, SC_RDM);
+  addSum_(sum, SC_SUB_MESSAGE);
+  addSum_(sum, 24 + length());
+  addSum_(sum, source.manufacturer);
+  addSum_(sum, source.device);
+  addSum_(sum, destination.manufacturer);
+  addSum_(sum, destination.device);
+  addSum_(sum, transaction);
+  addSum_(sum, portID);
+  addSum_(sum, messageCount);
+  addSum_(sum, subDevice);
+  addSum_(sum, commandClass);
+  addSum_(sum, parameterId);
+  addSum_(sum, length());
+  for (const auto &val : data_)
+    addSum_(sum, val);
 
   return sum;
 }
diff --git a/protocol/esta/rdm/message.h b/protocol/esta/rdm/message.h
index 4cb286c..41bed83 100644
--- a/protocol/esta/rdm/message.h
+++ b/protocol/esta/rdm/message.h
@@ -124,23 +124,29 @@ public: // templates
       data.push_back(raw[i]);
   }
 
+private: // templates
+  /**
+   * @brief addSum_
+   * @param sum
+   * @param val
+   */
   template<typename T>
-  uint16_t addSum_(uint16_t sum, const T val) const
+  static void addSum_(uint16_t &sum, const T &val)
   {
     uint16_t carry;
-    auto raw = reinterpret_cast<const uint8_t*>(&val);
+    auto raw = reinterpret_cast<const uint8_t*>(val);
     for (int i = sizeof(T);  --i >= 0; )
+    {
+      auto num = raw[i];
+      while (num != 0)
       {
-        uint8_t num = raw[i];
-        while (num != 0)
-          {
-            carry = sum & num;
-            sum = sum ^ num;
-            num = carry << 1;
-          }
+        carry = sum & num;
+        sum = sum ^ num;
+        num = carry << 1;
       }
-    return sum;
+    }
   }
+
 }; // struct Message