DBM authentication requiring AuthUserFile?

I need to secure a directory on the apache server, so I turned on dbm in the httpd.conf

LoadModule authn_dbm_module libexec/apache24/mod_authn_dbm.so

I created the DBM file, added a simple index.html file and added the following to the httpd-vhosts file:

<Directory "/home/tth/www/data/app">
  AuthName "restricted stuff"
  AuthType Basic
  AuthDBMUserFile "/home/tth/www/dbuser"
  require valid-user

restarted apache, the password screen pops up but then I get an internal server error and the following in the error_log:

[Sun Aug 20 10:37:32.882701 2017] [authn_file:error] [pid 85477] [client xx.xxx.
xxx.xxx:62870] AH01619: AuthUserFile not specified in the configuration

Any idea what I'm doing wrong here?
I have that what is a little unusual, if I use the htdbm command it works perfectly. If I use dbmmanage to create the file and add the user, it still errors out.