zypper package provider fails to downgrade packages

When specifying a specific version of a package (ensure => ...), the zypper provider tries to install that package using the command:

/usr/bin/zypper --quiet install --auto-agree-with-licenses --no-confirm <package>-<version>

This fails - running the command without the --quiet switch reveals the error:

The selected package '<package>-<version>' from repository 'Repository' has lower version than the installed one. Use 'zypper install --oldpackage <package>-<version>' to force installation of the package.

When ensure is set to install an older package than the installed package, the --oldpackage switch should be used. (I have not tested to determine whether it is safe to always specify that switch.)