diff --git a/DCCRMT.cpp b/DCCRMT.cpp
index 4c5fe4e..631cc16 100644
--- a/DCCRMT.cpp
+++ b/DCCRMT.cpp
@@ -21,6 +21,7 @@
 #include "defines.h"
 #include "DIAG.h"
 #include "DCCRMT.h"
+#include "DCCTimer.h"
 #include "DCCWaveform.h" // for MAX_PACKET_SIZE
 #include "soc/gpio_sig_map.h"
 
@@ -67,6 +68,8 @@ RMTChannel *channelHandle[8] = { 0 };
 void IRAM_ATTR interrupt(rmt_channel_t channel, void *t) {
   RMTChannel *tt = channelHandle[channel];
   if (tt) tt->RMTinterrupt();
+  if (channel == 0)
+    DCCTimer::updateMinimumFreeMemoryISR(0);
 }
 
 RMTChannel::RMTChannel(pinpair pins, bool isMain) {