A U.S. magistrate judge on Thursday said that Theranos Inc. should not be allowed to avoid an attempt by Walgreen Co. to recover $40 million it says it is owed after the embattled blood-testing company failed to deliver on its fundamental promise.

The recommendation from Chief Magistrate Judge Mary Pat Thynge of the District of Delaware came in response to Theranos' motion to dismiss part of a breach of contract suit Walgreens filed against its former business partner in November.

In its complaint, Walgreens said Theranos was required to repay a $40 million convertible note Walgreens had purchased in an agreement to operate “Theranos Wellness Centers” out of its stores. According to court documents, the deal was predicated on Theranos' ability to provide comprehensive blood testing with just a few drops of blood taken from a single stick to a patient's finger.