diff --git a/MySensors.h b/MySensors.h
index 8ef11988d..295888a7f 100644
--- a/MySensors.h
+++ b/MySensors.h
@@ -388,7 +388,6 @@ MY_DEFAULT_RX_LED_PIN in your sketch instead to enable LEDs
 #include "core/MySensorsCore.cpp"
 
 // HW mains
-#if !defined(MY_CORE_ONLY)
 #if defined(ARDUINO_ARCH_AVR)
 #include "hal/architecture/AVR/MyMainAVR.cpp"
 #elif defined(ARDUINO_ARCH_SAMD)
@@ -404,7 +403,6 @@ MY_DEFAULT_RX_LED_PIN in your sketch instead to enable LEDs
 #elif defined(TEENSYDUINO)
 #include "hal/architecture/Teensy3/MyMainTeensy3.cpp"
 #endif
-#endif
 
 #endif
 
diff --git a/core/MySensorsCore.cpp b/core/MySensorsCore.cpp
index 5412e87b9..fcb69398d 100644
--- a/core/MySensorsCore.cpp
+++ b/core/MySensorsCore.cpp
@@ -88,6 +88,14 @@ void _infiniteLoop(void)
 
 void _begin(void)
 {
+#if defined(MY_CORE_ONLY)
+	// initialize HW and run setup if present
+	(void)hwInit();
+	if (setup) {
+		setup();
+	}
+	return;
+#endif
 	// reset wdt
 	hwWatchdogReset();
 
diff --git a/examples/SecurityPersonalizer/SecurityPersonalizer.ino b/examples/SecurityPersonalizer/SecurityPersonalizer.ino
index 882d52366..58ae7593e 100644
--- a/examples/SecurityPersonalizer/SecurityPersonalizer.ino
+++ b/examples/SecurityPersonalizer/SecurityPersonalizer.ino
@@ -439,9 +439,7 @@ void setup()
 	hwRandomNumberInit();
 #endif
 
-	Serial.begin(MY_BAUD_RATE);
 	while(!Serial); // For USB enabled devices, wait for USB enumeration before continuing
-	hwInit();
 
 	print_greeting();