diff --git a/protocol/sacn/universe.cpp b/protocol/sacn/universe.cpp
index 9266012..2b18606 100644
--- a/protocol/sacn/universe.cpp
+++ b/protocol/sacn/universe.cpp
@@ -444,8 +444,8 @@ void Universe::tx_loop_()
   ///
   /// > \cite DMX Table 6 - Timing Diagram Values - output of transmitting UART
   /// >
-  /// > Minimum Update Time for 513 slots : 22.7ms
-  std::chrono::milliseconds minimum_update_time(23);
+  /// > Minimum Update Time for 513 slots : 22.7ms = 22700µs
+  std::chrono::microseconds minimum_update_time(22700);
 
   /// > \cite sACN 6.6.2 Null START Code Transmission Requirements in E1.31
   /// > Data Packets
@@ -469,8 +469,7 @@ void Universe::tx_loop_()
   while (enable || terminated_resend >= 0)
     {
       // enforce strict minimum update times
-      auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>
-          (std::chrono::system_clock::now() - last_sent);
+      auto elapsed = std::chrono::system_clock::now() - last_sent;
       if (elapsed < minimum_update_time)
         std::this_thread::sleep_for(minimum_update_time - elapsed);
 
@@ -479,7 +478,6 @@ void Universe::tx_loop_()
       enable = tx_enable_;
       tx_control_mutex_.unlock();
 
-
       if (enable)
         {
           if (active_data_slots)
@@ -494,26 +492,27 @@ void Universe::tx_loop_()
         }
 
       // see if this is new data or re-transmitting
-      auto sleep = std::chrono::milliseconds(minimum_update_time);
       null_start_mutex.lock();
       bool new_data = (null_start_data != last_null_data);
       null_start_mutex.unlock();
+      auto sleep = minimum_update_time;
       if (new_data)
         {
           retransmission_count = 0;
           last_null_data = null_start_data;
         }
-      else
-        if (++retransmission_count >= 2)
-          sleep = std::chrono::milliseconds(keep_alive_interval);
+      else if (++retransmission_count >= 2)
+        {
+          sleep = keep_alive_interval;
+          retransmission_count = 3;         // prevent counter from overflowing
+        }
 
       // send the sACN message
       sACNsend();
       last_sent = std::chrono::system_clock::now();
 
       // sleep before the next cycle
-      if (enable)
-        tx_request_.wait_for(mtx, sleep);
+      tx_request_.wait_for(mtx, sleep);
     }
 }