Problematic R version dependency when writing a package

I am writing a package using RStudio (Version 1.1.453) for my private use, nevertheless I use the discipline of R CMD Check. Currently I get this warning:

Dependence on R version ‘3.4.3’ not with patchlevel 0

In an attempt to avoid this problem I amended the relevant line in the DESCRIPTION file to read

Depends: R (>= 3.4)

and then ran R CMD Check again, and got the same warning. When I looked at the DESCRIPTION file again the relevant line read:

Depends: R (>= 3.4.3)

Something was putting it back to its previous form.

What can I do to get round this problem?

I am using devtools 2.0.2 and usethis 1.4.0