How to fix Error 187 on Windows 11

by

Windows 11 Error 187: “The Specified System Semaphore Name Was Not Found”

Why This Error Happens

Error 187 occurs when an application or system process attempts to open, signal, or release a named semaphore object that either doesn’t exist yet or has already been destroyed by another process. This typically happens due to race conditions during application startup/shutdown, corrupted installation files referencing outdated synchronization objects, or improper termination of a program that left orphaned references in the Windows Object Manager. It can also surface when third-party software (especially older applications) conflicts with Windows 11’s process handling or when Windows services start out of the expected sequence.

Step-by-Step Resolution Guide

  1. Identify the Source Application
    Open Event Viewer (eventvwr.msc) → navigate to Windows Logs > Application and System. Filter by Event ID 187 to find the exact process/service name (e.g., .exe or driver) generating the error, as this determines your next steps.

  2. Run System File Checker and DISM
    Open Command Prompt as Administrator and run:

   sfc /scannow

Followed by:

   DISM /Online /Cleanup-Image /RestoreHealth

This repairs corrupted system files that may be improperly handling semaphore creation.

  1. Check and Reorder Service Dependencies
    If the error points to a specific Windows service, open services.msc, locate the affected service, right-click → Properties → Dependencies tab. Ensure prerequisite services are set to Automatic and start before the affected service. Set the problematic service’s Startup type to “Automatic (Delayed Start)” to avoid race conditions.

  2. Reinstall or Repair the Offending Application
    If a third-party app is the culprit, go to Settings > Apps > Installed Apps, select the app, and choose Modify/Repair if available. If not, fully uninstall it, restart Windows 11, then reinstall the latest version from the vendor.

  3. Clear Orphaned Handles via Reboot in Clean Boot State
    Run msconfig → Selective Startup → uncheck Load startup items → restart. This clears any orphaned semaphore handles left by third-party startup programs and helps isolate whether the issue is startup-related.

Alternative or Verification Steps

  • Verify the fix: Reopen Event Viewer and monitor the Application/System logs for 24–48 hours to confirm Event ID 187 no longer appears, and confirm the previously affected application/service now starts without hanging or crashing.
  • Alternative fix: If the issue persists and is tied to a specific driver or legacy software, run the program in Compatibility Mode (right-click the .exe → Properties → Compatibility tab → select an earlier Windows version) or check the vendor’s site for a Windows 11–specific patch.