diff --git a/avdweb_Switch.cpp b/avdweb_Switch.cpp
index c5fd143..31c7a7b 100644
--- a/avdweb_Switch.cpp
+++ b/avdweb_Switch.cpp
@@ -21,6 +21,7 @@ WEBSITE: http://www.avdweb.nl/arduino/hardware-interfacing/simple-switch-debounc
 1.2.1    30-11-2018 bugfix. Initialize time variables in the constructor. Fixes false event if first call to poll was delayed
 1.2.2    18-10-2019 beep when a switch is pressed with using a setBeepAllCallback function
 1.2.3    03-04-2020 made public: deglitchPeriod, debouncePeriod, longPressPeriod, doubleClickPeriod
+1.2.4    14-07-2021 "static switchCallback_t _beepAllCallback = nullptr;" gives error with SAMD21, removed "= nullptr;"
 
 ..........................................DEGLITCHING..............................
 
diff --git a/avdweb_Switch.h b/avdweb_Switch.h
index 42eb267..e2a996f 100644
--- a/avdweb_Switch.h
+++ b/avdweb_Switch.h
@@ -58,7 +58,8 @@ class Switch
   switchCallback_t _longPressCallback = nullptr;
   switchCallback_t _doubleClickCallback = nullptr;
   switchCallback_t _singleClickCallback = nullptr;
-  static switchCallback_t _beepAllCallback = nullptr; // static function pointer, can be used by all objects
+  static switchCallback_t _beepAllCallback; // static function pointer, can be used by all objects 
+  //static switchCallback_t _beepAllCallback = nullptr; // gives error with SAMD21
   //static void(*_beepAllCallback)(void*) = nullptr; // static function pointer without typedef
   
   void* _pushedCallbackParam = nullptr;
@@ -66,6 +67,7 @@ class Switch
   void* _longPressCallbackParam = nullptr;
   void* _doubleClickCallbackParam = nullptr;
   void* _singleClickCallbackParam = nullptr;
-  static void* _beepAllCallbackParam = nullptr; // can be used by all objects
+  static void* _beepAllCallbackParam; // can be used by all objects
+  //static void* _beepAllCallbackParam = nullptr; // gives error with SAMD21
 };
 #endif