Microsoft Confirms KB5089549 Fails to Install With 0x800f0922 Error, Shares Temporary Fixes

Last week, Microsoft released May 2026 Patch Tuesday Update, KB5089549, for Windows 11 users with a few improvements, while also fixing the previously reported incorrect BitLocker Recovery prompts. In fact, the company has also confirmed the same issue in the changelog for the latest Windows 10 Extended Security Update.

Windows 11 May 2026 Patch KB5089549 installation fails with error code 0x800f0922, Microsoft confirms

Speaking of KB5089549, Microsoft has officially updated the changelog and acknowledged that some Windows 11 devices may fail to install the latest Patch Tuesday update. Apparently, the update may fail to complete installation with error code 0x800f0922, especially on devices with very limited free space inside the EFI System Partition (ESP).

According to Microsoft, the installation issue affects devices where the ESP has 10MB or less free storage available. What makes the situation confusing is that the update initially appears to install normally. However, during the restart phase, usually around 35–36% completion, Windows suddenly rolls back the installation.

As part of the rollback process, affected users may encounter the message: “Something didn’t go as planned. Undoing changes.” The installation then eventually fails with error code 0x800f0922.

Microsoft also noted that affected systems could generate CBS log entries pointing toward insufficient EFI partition storage. Some of the reported log messages include:

• SpaceCheck: Insufficient free space
• ServicingBootFiles failed. Error = 0x70
• SpaceCheck: used by third-party/OEM files outside of Microsoft boot directories​​​​​​​

The company has shared a few workarounds, though

If KB5089549 fails to install with 0x800f0922 error, you can try the following workarounds:

Option 1: Allow the update to install by modifying an ESP registry setting

1. Open Command Prompt as an administrator.
2. Run the following command:​​​​​​​ reg add “HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc /v EspPaddingPercent /t REG_DWORD /d 0 /f”​​​​​​​
3. Restart the affected device.
4. Retry installing the update.

Important Note: Editing the registry incorrectly can cause serious system problems. Therefore, Microsoft always recommends backing up the registry before making any changes.

Option 2: Mitigate the issue by using Known Issue Rollback (KIR)

Microsoft also confirms that the users facing the installation error can try Known Issue Rollback (KIR). For most consumer and unmanaged business devices, the fix reportedly rolls out automatically. Restarting the affected PC may help the mitigation apply faster. Meanwhile, enterprise-managed systems will require IT admins to manually deploy a dedicated Group Policy linked to KB5089549.

Fortunately, Microsoft says a permanent fix is currently in progress and will release as part of a future Windows update.