diff --git a/js/src/ion/Lowering.cpp b/js/src/ion/Lowering.cpp
index 47b79ec14d6..ef294b29648 100644
--- a/js/src/ion/Lowering.cpp
+++ b/js/src/ion/Lowering.cpp
@@ -300,9 +300,20 @@ LIRGenerator::visitCall(MCall *call)
     // Call known functions.
     if (target) {
         if (target->isNative()) {
-            LCallNative *lir = new LCallNative(argslot, tempFixed(CallTempReg0),
-                                               tempFixed(CallTempReg1), tempFixed(CallTempReg2),
-                                               tempFixed(CallTempReg3));
+            Register cxReg, numReg, vpReg, tmpReg;
+            GetTempRegForIntArg(0, 0, &cxReg);
+            GetTempRegForIntArg(1, 0, &numReg);
+            GetTempRegForIntArg(2, 0, &vpReg);
+
+            // Even though this is just a temp reg, use the same API to avoid
+            // register collisions.
+            mozilla::DebugOnly<bool> ok = GetTempRegForIntArg(3, 0, &tmpReg);
+            MOZ_ASSERT(ok, "How can we not have four temp registers?");
+
+            LCallNative *lir = new LCallNative(argslot, tempFixed(cxReg),
+                                               tempFixed(numReg),
+                                               tempFixed(vpReg),
+                                               tempFixed(tmpReg));
             return (defineReturn(lir, call) && assignSafepoint(lir, call));
         }