diff --git a/example/blink/platformio.ini b/example/blink/platformio.ini
index b0aba42..f1dfa79 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 -DUSB_SERIAL -DTEENSY_OPT_FASTER_LTO
+build_flags = -Wformat=1
 upload_flags = -v
 upload_protocol = teensy-cli
diff --git a/src/arduino_freertos.h b/src/arduino_freertos.h
index ed28533..18b1f9d 100644
--- a/src/arduino_freertos.h
+++ b/src/arduino_freertos.h
@@ -33,23 +33,14 @@
 
 #include "FreeRTOS.h"
 #include "task.h"
+#include "HardwareSerial.h"
 #include "Arduino.h"
 #include "Print.h"
 #if defined(__has_include) && __has_include("Wire.h")
 #include "Wire.h"
-#else
-class TwoWire;
-class Wire;
-class Wire1;
-class Wire2;
-class Wire3;
 #endif
 #if defined(__has_include) && __has_include("SPI.h")
 #include "SPI.h"
-#else
-class SPI;
-class SPI1;
-class SPI2;
 #endif
 #if defined(__has_include) && __has_include("FS.h")
 #include "FS.h"
@@ -132,8 +123,9 @@ using ::micros;
 using ::millis;
 using ::yield;
 
-using ::HardwareSerial;
 using ::Serial;
+#if !defined DISABLE_ARDUINO_HWSERIAL
+using ::HardwareSerial;
 using ::Serial1;
 using ::Serial2;
 using ::Serial3;
@@ -146,12 +138,14 @@ using ::Serial7;
 #ifdef ARDUINO_TEENSY41
 using ::Serial8;
 #endif
-#if defined(__has_include) && __has_include("SPI.h")
+#endif // !DISABLE_ARDUINO_HWSERIAL
+#if defined(__has_include) && __has_include("SPI.h") && !defined DISABLE_ARDUINO_SPI
 using ::SPI;
 using ::SPI1;
 using ::SPI2;
 #endif // SPI.h
 using ::Stream;
+#if defined(__has_include) && __has_include("Wire.h") && !defined DISABLE_ARDUINO_WIRE
 using ::TwoWire;
 using ::Wire;
 using ::Wire1;
@@ -159,6 +153,7 @@ using ::Wire2;
 #ifdef WIRE_IMPLEMENT_WIRE3
 using ::Wire3;
 #endif
+#endif // Wire.h
 
 using ::String;
 
diff --git a/src/portable/teensy_3.cpp b/src/portable/teensy_3.cpp
index 7f2339c..a721a8d 100644
--- a/src/portable/teensy_3.cpp
+++ b/src/portable/teensy_3.cpp
@@ -115,9 +115,13 @@ void yield() {
         }
     }
 #endif // USB_TRIPLE_SERIAL
+
+#if !defined DISABLE_ARDUINO_HWSERIAL
     if (yield_active_check_flags & YIELD_CHECK_HARDWARE_SERIAL) {
         HardwareSerial::processSerialEventsList();
     }
+#endif // !DISABLE_ARDUINO_HWSERIAL
+
     running = 0;
     if (yield_active_check_flags & YIELD_CHECK_EVENT_RESPONDER) {
         EventResponder::runFromYield();
diff --git a/src/portable/teensy_4.cpp b/src/portable/teensy_4.cpp
index 9840e0d..f3719bc 100644
--- a/src/portable/teensy_4.cpp
+++ b/src/portable/teensy_4.cpp
@@ -131,10 +131,12 @@ FLASHMEM void yield() {
     }
 #endif // USB_TRIPLE_SERIAL
 
+#if !defined DISABLE_ARDUINO_HWSERIAL
     // Current workaround until integrate with EventResponder.
     if (yield_active_check_flags & YIELD_CHECK_HARDWARE_SERIAL) {
         HardwareSerial::processSerialEventsList();
     }
+#endif // !DISABLE_ARDUINO_HWSERIAL
 
     running = 0;
     if (yield_active_check_flags & YIELD_CHECK_EVENT_RESPONDER) {
@@ -177,10 +179,12 @@ FLASHMEM void yield() {
     }
 #endif // USB_TRIPLE_SERIAL
 
+#if !defined DISABLE_ARDUINO_HWSERIAL
     // Current workaround until integrate with EventResponder.
     if (check_flags & YIELD_CHECK_HARDWARE_SERIAL) {
         HardwareSerial::processSerialEventsList();
     }
+#endif // !DISABLE_ARDUINO_HWSERIAL
 
     running = 0;
     if (check_flags & YIELD_CHECK_EVENT_RESPONDER) {