I'm getting a fatal error when trying to run "composer update" or "composer install":

Fatal error: Call to undefined method Composer\Package\RootAliasPackage::setStabilityFlags() in ....web\vendor\wikimedia\composer-merge-plugin\src\MergePlugin.php on line 312

Looking at the code, the function mergeStabilityFlags takes RootPackageInterface as its argument, but this interface doesn't have method setStabilityFlags. It exists only in RootPackage, but not in RootAliasPackage (both implement RootPackageInterface).

I don't fully understand how this works in composer and when RootAliasPackage is used instead of RootPackage, so can't fix it properly. I can add if ($root instanceof RootPackage) in mergeStabilityFlags, but not sure if it's really correct fix.