Fix ERROR_FLT_MUST_BE_NONPAGED_POOL (0X801F000C) on Windows

The 30-Second Fix: Check Your Filter Drivers

You're probably seeing this error pop up in Event Viewer or a blue screen. It's almost always a third-party filter driver—antivirus, backup software, disk encryption, or a file system filter—that's trying to use paged memory when the system needs nonpaged pool. The quickest way to confirm is to open Event Viewer, go to Windows Logs > System, and look for entries with source FltMgr or storport. If you see the error code 0X801F000C next to a driver name like xxdisk.sys or cbfsconnect.sys, that's your culprit.

Here's what I do first—disable the suspected driver temporarily. Go to Device Manager, find the device (e.g., your storage controller or a virtual drive), right-click, and select Disable device. Reboot. If the error stops, you've found the problem. Re-enable it, then update or uninstall the driver from the manufacturer's site. Had a client last month whose print queue died because of an old SonicWall VPN filter driver that was doing exactly this—disabled it, error gone, reinstalled the latest version, good as new.

The 5-Minute Fix: Registry Tweak for Nonpaged Pool

If disabling doesn't help, or you can't identify the driver, the next step is to force the filter manager to use nonpaged pool. This is a registry change that tells the system to allocate memory differently for certain contexts. Back up your registry first—I've seen people skip this and brick their install.

1. Press Win + R, type regedit, hit Enter.
2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FltMgr.
3. If you don't see a Parameters key, right-click FltMgr, select New > Key, name it Parameters.
4. Inside Parameters, create a new DWORD (32-bit) value called UseNonPagedPool.
5. Set its value to 1 (hexadecimal).
6. Close regedit and reboot.

This forces the filter manager to allocate nonpaged pool for all contexts. It's not a permanent fix for bad drivers, but it'll stabilize the system until you can update the offending software. I've used this on a Server 2019 box that was blue-screening every hour with a Veritas backup filter—stopped dead after this tweak.

The 15+ Minute Fix: Driver Verifier and Cleanup

If you're still seeing the error, it's time to dig deeper. The problem is likely a driver that's borderline broken—maybe it passes basic certification but hits this pool issue under load. Driver Verifier is your weapon.

1. Open Command Prompt as Administrator.
2. Type verifier and press Enter. Select Create custom settings (for code developers).
3. Choose Select individual settings, then check Special pool, Force IRQL checking, and Pool tracking. Click Next.
4. Select Select driver names from a list. Click Next, then Unsign all drivers from the top. Wait for the list to load.
5. Look for any filter drivers (often named with *.sys and belonging to third-party apps). Select them. Avoid Microsoft drivers unless you're sure.
6. Click Finish and reboot. The system will run slower—that's normal. It'll crash with a more detailed bugcheck that pinpoints the exact driver.

After the crash, boot into Safe Mode, open verifier again, select Delete existing settings, and reboot normally. Then uninstall or update the driver Verifier flagged.

Pro tip: I've seen this error on systems with Malwarebytes and Acronis True Image filter drivers. If you have either, uninstall them completely (not just disable) and see if it clears up. Reinstall the latest version from their site—old builds had known issues with nonpaged pool.

Still stuck?

If none of this works, run sfc /scannow and dism /online /cleanup-image /restorehealth to rule out system file corruption. Then check for a BIOS update—some storage controllers (especially NVMe) have buggy firmware that triggers this with certain filter drivers. A client on a Dell Precision 5820 had this exact error after a Windows update; a BIOS update from Dell fixed it. No joke.