diff --git a/src/fensterPiepser_NodeMCU_32S.cpp b/src/fensterPiepser_NodeMCU_32S.cpp
index 1601c5b..3e248f8 100644
--- a/src/fensterPiepser_NodeMCU_32S.cpp
+++ b/src/fensterPiepser_NodeMCU_32S.cpp
@@ -69,10 +69,10 @@
 uint32_t gtMillis;
 char textBuf[100];
 DeciSeconds_t waitTimeDs = 0; /* in deciSeconds */
-DeciSeconds_t tDecis   = 0;
+volatile DeciSeconds_t tDecis   = 0;
 uint8_t numberWindowsOpen = 0;
 ReceiverFunkThermometerData_t thermoData = {0, 0};
-bool   bRequestShortBeep = false;
+volatile bool bRequestShortBeep = false;
 bool   bIsNightTime = false;
 
 PiepPattern *piepPattern;