Google was hit with a record-breaking $2.7 billion fine last month by the European Commission for breaking antitrust laws. The EU says Google demoted rivals and unfairly promoted its own services in search results related to shopping. While the fine is the largest antitrust judgement ever, an even bigger fine could be on the way for Google.

Reuters reports that EU regulators are considering another record-breaking fine for Google over its Android operating system. The European Commission has been investigating Android after rivals complained that Google has been abusing its market dominance. Google has been accused of limiting access to the Google Play Store unless phone makers also bundle Google search and Chrome apps. Google has also reportedly blocked phone makers from creating devices that run forked versions of Android, as part of an anti-fragmentation agreement.

While Reuters suggests the potential Android fine could top the $2.7 billion penalty, a bigger concern for Google will be whether it’s forced to dramatically alter Android and unbundle key parts. Android has long been considered as open source software, but Google has slowly been adding key components into its Google Play Services software and associated agreements.

Google’s predicament sounds similar to Microsoft’s own fight with the EU more than 10 years ago. Microsoft was accused of bundling its Windows Media Player with Windows, and the EU forced it to unbundle the app. Microsoft created a special version of Windows for Europe without the app. Microsoft was also accused of bundling its Internet Explorer browser with Windows, and the EU forced the company to include a browser ballot with non-Microsoft browsers in an effort to improve competition.

EU antitrust regulators have now appointed a peer review panel, according to Reuters. The review includes a panel of experts that will give a second opinion on the EU’s plans. A decision on Google’s Android case in the EU is expected by the end of the year.