diff --git a/src/hal/hal_esp32.cpp b/src/hal/hal_esp32.cpp
index ace7626..21367b9 100755
--- a/src/hal/hal_esp32.cpp
+++ b/src/hal/hal_esp32.cpp
@@ -346,7 +346,7 @@ bool HAL_ESP32::wait(WaitKind waitKind)
 }
 
 // Gets current time in LMIC ticks
-u4_t hal_ticks()
+u4_t IRAM_ATTR hal_ticks()
 {
     // LMIC tick unit: 16µs
     // esp_timer unit: 1µs