diff --git a/cores/arduino/delay.c b/cores/arduino/delay.c
index ea000abb0..19aed212f 100644
--- a/cores/arduino/delay.c
+++ b/cores/arduino/delay.c
@@ -26,7 +26,7 @@ extern "C" {
 /** Tick Counter united by ms */
 static volatile uint32_t _ulTickCount=0 ;
 
-uint32_t millis( void )
+unsigned long millis( void )
 {
 // todo: ensure no interrupts
   return _ulTickCount ;
@@ -36,7 +36,7 @@ uint32_t millis( void )
 // Theory: repeatedly take readings of SysTick counter, millis counter and SysTick interrupt pending flag.
 // When it appears that millis counter and pending is stable and SysTick hasn't rolled over, use these
 // values to calculate micros. If there is a pending SysTick, add one to the millis counter in the calculation.
-uint32_t micros( void )
+unsigned long micros( void )
 {
   uint32_t ticks, ticks2;
   uint32_t pend, pend2;
@@ -61,7 +61,7 @@ uint32_t micros( void )
   // a runtime multiplication and shift, saving a few cycles
 }
 
-void delay( uint32_t ms )
+void delay( unsigned long ms )
 {
   if ( ms == 0 )
   {
diff --git a/cores/arduino/delay.h b/cores/arduino/delay.h
index 1df845bd7..be3a93c65 100644
--- a/cores/arduino/delay.h
+++ b/cores/arduino/delay.h
@@ -33,7 +33,7 @@ extern "C" {
  *
  * \return Number of milliseconds since the program started (uint32_t)
  */
-extern uint32_t millis( void ) ;
+extern unsigned long millis( void ) ;
 
 /**
  * \brief Returns the number of microseconds since the Arduino board began running the current program.
@@ -45,7 +45,7 @@ extern uint32_t millis( void ) ;
  *
  * \note There are 1,000 microseconds in a millisecond and 1,000,000 microseconds in a second.
  */
-extern uint32_t micros( void ) ;
+extern unsigned long micros( void ) ;
 
 /**
  * \brief Pauses the program for the amount of time (in miliseconds) specified as parameter.
@@ -53,15 +53,15 @@ extern uint32_t micros( void ) ;
  *
  * \param dwMs the number of milliseconds to pause (uint32_t)
  */
-extern void delay( uint32_t dwMs ) ;
+extern void delay( unsigned long dwMs ) ;
 
 /**
  * \brief Pauses the program for the amount of time (in microseconds) specified as parameter.
  *
  * \param dwUs the number of microseconds to pause (uint32_t)
  */
-static __inline__ void delayMicroseconds( uint32_t ) __attribute__((always_inline, unused)) ;
-static __inline__ void delayMicroseconds( uint32_t usec )
+static __inline__ void delayMicroseconds( unsigned int ) __attribute__((always_inline, unused)) ;
+static __inline__ void delayMicroseconds( unsigned int usec )
 {
   if ( usec == 0 )
   {