diff --git a/example/blink/platformio.ini b/example/blink/platformio.ini
index f1dfa79..b0aba42 100644
--- a/example/blink/platformio.ini
+++ b/example/blink/platformio.ini
@@ -30,6 +30,6 @@ platform = https://github.com/tsandmann/platform-teensy.git
 board = teensy41
 framework = arduino
 lib_deps = https://github.com/tsandmann/freertos-teensy.git
-build_flags = -Wformat=1
+build_flags = -Wformat=1 -DUSB_SERIAL -DTEENSY_OPT_FASTER_LTO
 upload_flags = -v
 upload_protocol = teensy-cli
diff --git a/library.json b/library.json
index 14f0be6..bd719f1 100644
--- a/library.json
+++ b/library.json
@@ -8,7 +8,7 @@
     "type": "git",
     "url": "https://github.com/tsandmann/freertos-teensy"
   },
-  "version": "10.5.1-8",
+  "version": "10.5.1-9",
   "authors": [
     {
       "name": "Richard Barry",
diff --git a/library.properties b/library.properties
index 2b88d80..fdfa0bb 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=freertos-teensy
-version=10.5.1-8
+version=10.5.1-9
 author=Richard Barry <info@freertos.org>
 maintainer=Timo Sandmann
 sentence=<h3>FreeRTOS Real Time Operating System implemented for Teensy (3.5, 3.6, 4.0, 4.1).</h3>
diff --git a/src/portable/teensy_4.cpp b/src/portable/teensy_4.cpp
index f3719bc..7112cc1 100644
--- a/src/portable/teensy_4.cpp
+++ b/src/portable/teensy_4.cpp
@@ -33,6 +33,7 @@
 #include "event_responder_support.h"
 #include "avr/pgmspace.h"
 #include "EventResponder.h"
+#include "imxrt.h"
 
 #define __ASM __asm
 #define __STATIC_INLINE static inline
@@ -182,7 +183,11 @@ FLASHMEM void yield() {
 #if !defined DISABLE_ARDUINO_HWSERIAL
     // Current workaround until integrate with EventResponder.
     if (check_flags & YIELD_CHECK_HARDWARE_SERIAL) {
+#ifdef FLEXIO_TIMCFG_STARTBIT_DISABLED // workaround to check for Teensyduino >= 1.59 Beta 4
+        HardwareSerialIMXRT::processSerialEventsList();
+#else
         HardwareSerial::processSerialEventsList();
+#endif
     }
 #endif // !DISABLE_ARDUINO_HWSERIAL