diff --git a/Source/timers.c b/Source/timers.c
index 95ee47b..69e2238 100644
--- a/Source/timers.c
+++ b/Source/timers.c
@@ -241,7 +241,7 @@
 }
 /*-----------------------------------------------------------*/
 
-portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, portBASE_TYPE *pxHigherPriorityTaskWoken, portTickType xBlockTime )
+portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, signed portBASE_TYPE *pxHigherPriorityTaskWoken, portTickType xBlockTime )
 {
 portBASE_TYPE xReturn = pdFAIL;
 xTIMER_MESSAGE xMessage;