diff --git a/src/CollarRx.cpp b/src/CollarRx.cpp
index cb172e9..5766e78 100644
--- a/src/CollarRx.cpp
+++ b/src/CollarRx.cpp
@@ -82,7 +82,7 @@ void CollarRx::rx_start()
   attachInterrupt(digitalPinToInterrupt(_rx_pin), CollarRx::s_isr, RISING);
 }
 
-void CollarRx::s_isr()
+IRAM_ATTR void CollarRx::s_isr()
 {
   _instance->isr();
 }
diff --git a/src/type1/CollarRxType1.cpp b/src/type1/CollarRxType1.cpp
index 194b966..d9b7231 100644
--- a/src/type1/CollarRxType1.cpp
+++ b/src/type1/CollarRxType1.cpp
@@ -50,7 +50,7 @@ bool CollarRxType1::is_message_valid(const uint8_t buffer[5])
   return true;
 }
 
-void CollarRxType1::isr()
+IRAM_ATTR void CollarRxType1::isr()
 {
   static unsigned long rx_micros =0;
   static uint8_t pulse_count = 0;
diff --git a/src/type2/CollarRxType2.cpp b/src/type2/CollarRxType2.cpp
index 96643f7..92c78f8 100644
--- a/src/type2/CollarRxType2.cpp
+++ b/src/type2/CollarRxType2.cpp
@@ -97,7 +97,7 @@ bool CollarRxType2::buffer_to_collar_message(const uint8_t buffer[5], struct col
   return is_valid;
 }
 
-void CollarRxType2::isr()
+IRAM_ATTR void CollarRxType2::isr()
 {
   static unsigned long rx_micros =0;
   static uint8_t pulse_count = 0;