Christmas lights may cause Wi-Fi to slow down this holiday season. A Wi-Fi checker app, developed by Ofcom, a British telecommunications regulator, was released Tuesday. The app is used to determine the speed of a user’s connection. Noted in the app are a few things that can disrupt Wi-Fi signals, with Christmas lights named among them.

NBC News reports that the app also listed TV monitors and stereo speakers as devices that can disrupt a wireless Internet signal. Daniel Carpini, vice president of marketing at xG Technology, a company that creates interference-free Wi-Fi for the U.S Military and others says, “It’s possible that your Christmas lights will have some effect on your router and broadband performance.”

While Christmas lights will not cause as much interference as high-frequency items such as microwaves or cordless phones, they still emit an electromagnetic field that may cause disruptions. A spokesperson for Linksys, a wireless router manufacturer says that, unless you use lights with unshielded wires, “It’s unlikely to be noticeable or detectable, unless you wrapped the lights around your Wi-Fi clients.”

Interference to the Wi-Fi signal would only occur when the lights are on. It is recommended that the lights are turned off when not in use, which is also beneficial to those trying to conserve energy. Moving interfering devices at least a foot away from routers should cut down on any possible interference.

A Cisco spokesperson warns that interference from Christmas lights controlled via Wi-Fi pose a greater risk of disruption than traditional Christmas lights.