diff --git a/src/modules/SX128x/SX128x.cpp b/src/modules/SX128x/SX128x.cpp
index 37b93619..3d1ce145 100644
--- a/src/modules/SX128x/SX128x.cpp
+++ b/src/modules/SX128x/SX128x.cpp
@@ -327,8 +327,8 @@ int16_t SX128x::transmit(const uint8_t* data, size_t len, uint8_t addr) {
   int16_t state = standby();
   RADIOLIB_ASSERT(state);
 
-  // calculate timeout in ms (500% of expected time-on-air)
-  RadioLibTime_t timeout = (getTimeOnAir(len) * 5) / 1000;
+  // calculate timeout in ms (5ms + 500 % of expected time-on-air)
+  RadioLibTime_t timeout = 5 + (getTimeOnAir(len) * 5) / 1000;
   RADIOLIB_DEBUG_BASIC_PRINTLN("Timeout in %lu ms", timeout);
 
   // start transmission