diff --git a/src/include/lwip/arch.h b/src/include/lwip/arch.h
index 6b541d89..41b123f6 100644
--- a/src/include/lwip/arch.h
+++ b/src/include/lwip/arch.h
@@ -106,7 +106,7 @@ typedef uintptr_t mem_ptr_t;
 #define X32_F PRIx32
 #endif
 #ifndef SZT_F
-#define SZT_F PRIuMAX
+#define SZT_F PRIuPTR
 #endif
 #endif