Different decimal separator for doubles in client and server side activities

I have trouble with server and client activitys expecting different decimal separators for doubles. Server side expects point, while client side expects comma.

To illustrate, I have setup a workflow with a declared variable of type Double, and whth default value 3.87. Inside Workflow Designer, the workflow runs fine, but when I try to run the workflow from a Essentials site (on the same machine), it won't run at all because it can't  assign a value of 3.87 to a double datatype variable.

I have tried to alter the regional settings, but without success. Does anyone know why I'm experiencing this, and which settings that can be adjusted to get this to work right?

Jostein