Why can't I call method InvokeServer on remote functions? [SOLVED]

The server side:

local remoteWalk = Instance.new("RemoteFunction")
local remoteRun = Instance.new("RemoteFunction")

local function Walk(client)

    stats.human.WalkSpeed = 16  --stats.human refers to a player's humanoid

end

local function Run(client)

    stats.human.WalkSpeed = 32

end

remoteWalk.OnServerInvoke = Walk
remoteRun.OnServerInvoke = Run

The following code is in a module script, which is required by a local script.

local requests = ActionManager.ActionRequests   --A table containing the remote functions

local remoteWalk = requests["Walk"] --the "Walk" remote function from the server script
local remoteRun = requests["Run"]       --the "Run" remote function from the server script

local function Walk()

    remoteWalk:InvokeServer()

end

local function Run()

    remoteRun:InvokeServer()

end

--The "Walk" and "Run" functions are bound to keyboard inputs

I've simplified the code a bit to make it more readable. When the remote functions are invoked by the client, I get this error:

"Trying to call method on object type: 'RemoteFunction' with incorrect arguments."

I thought that was because I previously hadn't included a "client" argument on the server side, but I still get the same error. Could it be because the code is required from a module script? It's definitely being performed on the client. Thanks for the help!