https://github.com/webpack/webpack/blob/master/lib/HotModuleReplacementPlugin.js#L199 is looking for two arguments and otherwise it leaves the module id unaltered. This causes the module to be not be declined as the moduleId check is expecting an internal module id:
https://github.com/webpack/webpack/blob/master/lib/HotModuleReplacement.runtime.js#L253

From the docs it also looks like this function fails in the same way for array entry types.