diff --git a/ports/pic16bit/Makefile b/ports/pic16bit/Makefile
index 6d061514f958..dda48fa3ce5f 100644
--- a/ports/pic16bit/Makefile
+++ b/ports/pic16bit/Makefile
@@ -7,7 +7,7 @@ QSTR_DEFS = qstrdefsport.h
 include $(TOP)/py/py.mk
 include $(TOP)/extmod/extmod.mk
 
-XCVERSION ?= 1.35
+XCVERSION ?= 2.10
 XC16 ?= /opt/microchip/xc16/v$(XCVERSION)
 CROSS_COMPILE ?= $(XC16)/bin/xc16-
 
@@ -31,7 +31,7 @@ CFLAGS += -O1 -DNDEBUG
 endif
 
 LDFLAGS += --heap=0 -nostdlib -T $(XC16)/support/$(PARTFAMILY)/gld/p$(PART).gld -Map=$@.map --cref -p$(PART)
-LIBS += -L$(XC16)/lib -L$(XC16)/lib/$(PARTFAMILY) -lc -lm -lpic30
+LIBS += -L$(XC16)/lib -L$(XC16)/lib/$(PARTFAMILY) -lc99-elf -lm-elf -lc99-pic30-elf
 
 SRC_C = \
 	main.c \
diff --git a/ports/pic16bit/mpconfigport.h b/ports/pic16bit/mpconfigport.h
index a2d607fb2932..d80f7edb9e54 100644
--- a/ports/pic16bit/mpconfigport.h
+++ b/ports/pic16bit/mpconfigport.h
@@ -93,7 +93,3 @@ typedef int mp_off_t;
 #define MICROPY_MPHALPORT_H "pic16bit_mphal.h"
 #define MICROPY_HW_BOARD_NAME "dsPICSK"
 #define MICROPY_HW_MCU_NAME "dsPIC33"
-
-// XC16 toolchain doesn't seem to define these
-typedef int intptr_t;
-typedef unsigned int uintptr_t;
diff --git a/py/misc.h b/py/misc.h
index 96b13c151a6b..8ac80bb7b3e3 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -380,6 +380,18 @@ static inline bool mp_check(bool value) {
 
 // mp_int_t can be larger than long, i.e. Windows 64-bit, nan-box variants
 static inline uint32_t mp_clz_mpi(mp_int_t x) {
+    #ifdef __XC16__
+    mp_uint_t mask = MP_OBJ_WORD_MSBIT_HIGH;
+    mp_uint_t zeroes = 0;
+    while (mask != 0) {
+        if (mask & (mp_uint_t)x) {
+            break;
+        }
+        zeroes++;
+        mask >>= 1;
+    }
+    return zeroes;
+    #else
     MP_STATIC_ASSERT(sizeof(mp_int_t) == sizeof(long long)
         || sizeof(mp_int_t) == sizeof(long));
 
@@ -389,6 +401,7 @@ static inline uint32_t mp_clz_mpi(mp_int_t x) {
     } else {
         return mp_clzll((unsigned long long)x);
     }
+    #endif
 }
 
 #endif // MICROPY_INCLUDED_PY_MISC_H