Ruger has announced a recall of all Mark IV pistols—including the includes Ruger Mark IV Target, Hunter, Competition, 22/45, 22/45 Lite and 22/45 Tactical models—made before June 1, 2017 after discovering that some pistols could discharge unintentionally if the safety “isn’t utilized correctly.” More via the press release:

In particular, if the trigger is pulled while the safety lever is midway between the “safe” and “fire” positions (that is, the safety is not fully engaged or fully disengaged), the pistol may not fire when the trigger is pulled. However, if the trigger is released and the safety lever is then moved from the mid position to the “fire” position, the pistol may fire at that time.

While only a small percentage of Mark IV pistols are affected and no injuries have been reported, Ruger is erring on the side of caution and offering to retrofit all potentially affected pistols with an updated safety mechanism, completely free of charge.

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If your Ruger Mark IV pistol has a serial number beginning with “401” (2017 models) or “WBR” (2016 models), then it is subject to this recall. If your Mark IV has a serial number beginning with “500,” then it is not affected by the recall. Head on over to the Ruger Mark IV recall website at Ruger.com/MarkIVRecall to look up your pistol’s serial number.

All Ruger Mark IV pistols will be retrofitted on a  first-come, first-served basis, the company says. When a pistol is ready to be retrofitted, you’ll get a prepaid USPS box with a shipping label, along with packaging and shipping instructions. You only need to return the grip frame assembly to Ruger. Ruger will install the safety mechanism and return the grip frame assembly at no cost to you. The company is also throwing in a free magazine as a way of saying thank you during this process. Ruger says it’ll aim to return each pistol within a week of the day it arrives.