--- a/js/src/vm/UnboxedObject.cpp
+++ b/js/src/vm/UnboxedObject.cpp
@@ -104,16 +104,20 @@ UnboxedLayout::makeConstructorCode(JSCon
     regs.take(propertiesReg);
     regs.take(newKindReg);
     Register object = regs.takeAny(), scratch1 = regs.takeAny(), scratch2 = regs.takeAny();
 
     LiveGeneralRegisterSet savedNonVolatileRegisters = SavedNonVolatileRegisters(regs);
     for (GeneralRegisterForwardIterator iter(savedNonVolatileRegisters); iter.more(); ++iter)
         masm.Push(*iter);
 
+    // The scratch double register might be used by MacroAssembler methods.
+    if (ScratchDoubleReg.volatile_())
+        masm.push(ScratchDoubleReg);
+
     Label failure, tenuredObject, allocated;
     masm.branch32(Assembler::NotEqual, newKindReg, Imm32(GenericObject), &tenuredObject);
     masm.branchTest32(Assembler::NonZero, AbsoluteAddress(group->addressOfFlags()),
                       Imm32(OBJECT_FLAG_PRE_TENURE), &tenuredObject);
 
     // Allocate an object in the nursery
     masm.createGCObject(object, scratch1, templateObject, gc::DefaultHeap, &failure,
                         /* initFixedSlots = */ false);
@@ -201,16 +205,18 @@ UnboxedLayout::makeConstructorCode(JSCon
 
     Label done;
     masm.bind(&done);
 
     if (object != ReturnReg)
         masm.movePtr(object, ReturnReg);
 
     // Restore non-volatile registers which were saved on entry.
+    if (ScratchDoubleReg.volatile_())
+        masm.pop(ScratchDoubleReg);
     for (GeneralRegisterBackwardIterator iter(savedNonVolatileRegisters); iter.more(); ++iter)
         masm.Pop(*iter);
 
     masm.abiret();
 
     masm.bind(&failureStoreOther);
 
     // There was a failure while storing a value which cannot be stored at all
@@ -645,17 +651,20 @@ UnboxedPlainObject::createWithProperties
         return nullptr;
 
     for (size_t i = 0; i < layout.properties().length(); i++) {
         if (!obj->setValue(cx, layout.properties()[i], properties[i].value))
             return NewPlainObjectWithProperties(cx, properties, layout.properties().length(), newKind);
     }
 
 #ifndef JS_CODEGEN_NONE
-    if (cx->isJSContext() && !layout.constructorCode()) {
+    if (cx->isJSContext() &&
+        !layout.constructorCode() &&
+        cx->asJSContext()->runtime()->jitSupportsFloatingPoint)
+    {
         if (!UnboxedLayout::makeConstructorCode(cx->asJSContext(), group))
             return nullptr;
     }
 #endif
 
     return obj;
 }