diff --git a/include/FreeRTOS.h b/include/FreeRTOS.h
index 4b59512c9..7810b29d4 100644
--- a/include/FreeRTOS.h
+++ b/include/FreeRTOS.h
@@ -29,6 +29,12 @@
 #ifndef INC_FREERTOS_H
 #define INC_FREERTOS_H
 
+/*
+ * On Microchip xc16 target there will be undefined reference to _Nop
+ * xc.h is supplied by Microchip and defines Nop
+ */
+#include <xc.h>
+
 /*
  * Include the generic headers required for the FreeRTOS port being used.
  */
diff --git a/portable/MPLAB/PIC24_dsPIC/portmacro.h b/portable/MPLAB/PIC24_dsPIC/portmacro.h
index fbac471d5..9e1e3edf7 100644
--- a/portable/MPLAB/PIC24_dsPIC/portmacro.h
+++ b/portable/MPLAB/PIC24_dsPIC/portmacro.h
@@ -54,7 +54,10 @@
 #define portSTACK_TYPE  uint16_t
 #define portBASE_TYPE   short
 #define portPOINTER_SIZE_TYPE size_t
+/* Microchip xc16 compilers already define SIZE_MAX in stdint.h */
+#ifndef SIZE_MAX
 #define SIZE_MAX    ( ( size_t ) -1 )
+#endif
 
 typedef portSTACK_TYPE StackType_t;
 typedef short BaseType_t;