Plot does not update with a string vector as an observable in Makie


I tried to use a vector of strings as an Observable and the text! command to interactively update a plot in Makie. Here is an example:

using GLMakie

string_vec = Observable(["a", "b"])
string_test = Observable("changeable")

fig = Figure()
text!(string_vec, position=[(1,1), (1.2, 1)])
text!(string_test, position=(1.1, 0.5))

string_vec[] = ["c", "d"] # not updating the plot
string_test[] = "worked!"

It only works with a string as the observable, but not with a vector of strings. Do you have an idea what I am doing wrong? Many thanks!