diff --git a/js/src/jsnum.h b/js/src/jsnum.h
index c171bb572dea..290d893e10a1 100644
--- a/js/src/jsnum.h
+++ b/js/src/jsnum.h
@@ -363,7 +363,8 @@ ValueToUint16(JSContext *cx, const js::Value &v, uint16_t *out)
 static inline int32
 js_DoubleToECMAInt32(jsdouble d)
 {
-#if defined(__i386__) || defined(__i386)
+#if defined(__i386__) || defined(__i386) || defined(__x86_64__) || \
+    defined(_M_IX86) || defined(_M_X64)
     jsdpun du, duh, two32;
     uint32 di_h, u_tmp, expon, shift_amount;
     int32 mask32;