diff --git a/js/public/Value.h b/js/public/Value.h
index 272d9b478d..bc0fd0ec72 100644
--- a/js/public/Value.h
+++ b/js/public/Value.h
@@ -229,7 +229,11 @@ static inline JS::Value PoisonedObjectValue(JSObject* obj);
 namespace detail {
 
 constexpr int CanonicalizedNaNSignBit = 0;
+#if defined(__mips__) && !defined(__mips_nan2008)
+constexpr uint64_t CanonicalizedNaNSignificand = 0x7FFFFFFFFFFFFULL;
+#else
 constexpr uint64_t CanonicalizedNaNSignificand = 0x8000000000000ULL;
+#endif
 
 constexpr uint64_t CanonicalizedNaNBits =
     mozilla::SpecificNaNBits<double,