Days after arch-rival Amazon announced plans to buy Whole Foods for $13.7 billion, Walmart is apparently ramping up its defense.

That acquisition takes square aim at Walmart’s bread-and-butter grocery business by giving the online retailer 465 new retail locations—thus a much bigger brick-and-mortar presence.

Now, Walmart is telling some partners and suppliers that their software services should not run on Amazon Web Services cloud infrastructure, according to the Wall Street Journal.

The report quoted Bob Muglia, CEO of Snowflake Computing, saying that a Walmart (wmt, +0.98%) partner wanted to use his company’s data warehouse service, but was told it had to run on Microsoft (msft, +0.63%) Azure cloud instead of AWS.

Source: Walmart Gears Up Anti-Amazon Stance in Wake of Whole Foods Deal