diff --git a/Source/portable/IAR/ARM_CM3/port.c b/Source/portable/IAR/ARM_CM3/port.c
index 5059de372..be91fdfb3 100644
--- a/Source/portable/IAR/ARM_CM3/port.c
+++ b/Source/portable/IAR/ARM_CM3/port.c
@@ -200,7 +200,7 @@ void xPortSysTickHandler( void )
 void prvSetupTimerInterrupt( void )
 {
 	/* Configure SysTick to interrupt at the requested rate. */
-	*(portNVIC_SYSTICK_LOAD) = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
+	*(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
 	*(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
 }
 /*-----------------------------------------------------------*/