--- js/src/vm/JSONPrinter.cpp.orig	2020-05-12 17:06:38.387691368 +0900
+++ js/src/vm/JSONPrinter.cpp	2020-05-12 17:10:20.842391283 +0900
@@ -119,7 +119,8 @@ void JSONPrinter::property(const char* n
   out_.printf("%" PRIu64, value);
 }
 
-#if defined(XP_DARWIN) || defined(__OpenBSD__)
+#if defined(XP_DARWIN) || defined(__OpenBSD__) || \
+    (defined(__NetBSD__) && defined(__arm__))
 void JSONPrinter::property(const char* name, size_t value) {
   propertyName(name);
   out_.printf("%zu", value);
--- js/src/vm/JSONPrinter.h.orig	2020-05-12 17:06:42.908461670 +0900
+++ js/src/vm/JSONPrinter.h	2020-05-12 17:09:54.171126154 +0900
@@ -45,7 +45,8 @@ class JSONPrinter {
   void property(const char* name, uint32_t value);
   void property(const char* name, int64_t value);
   void property(const char* name, uint64_t value);
-#if defined(XP_DARWIN) || defined(__OpenBSD__)
+#if defined(XP_DARWIN) || defined(__OpenBSD__) || \
+    (defined(__NetBSD__) && defined(__arm__))
   // On OSX and OpenBSD, size_t is long unsigned, uint32_t is unsigned, and
   // uint64_t is long long unsigned. Everywhere else, size_t matches either
   // uint32_t or uint64_t.