Windows 10 DISM Error 87: Fixing “The Parameter Is Incorrect” When Running Repair Commands

A guide tells you to run DISM to repair Windows. You type the command, press Enter, and immediately see “Error: 87. The restorehealth option is unknown” or “The parameter is incorrect.” When dewaasia Windows 10 DISM error 87 appears, the repair never even starts.

DISM, the Deployment Image Servicing and Management tool, is strict about how commands are typed. Error 87 almost always means the command itself was not understood.

The most common reasons are missing spaces, using the wrong kind of Command Prompt, or a version of DISM that does not support the option.

Correcting the command usually fixes the error in seconds.

The error often appears when following repair instructions in a hurry, especially when commands are copied from a phone screen or a forum post.

What Might Be Causing It

DISM error 87 appears for these reasons:

• A space is missing before a slash, for example /Online/Cleanup-Image instead of /Online /Cleanup-Image.
• Command Prompt was not opened as administrator.
• Text was copied from a website with special characters that look like normal dashes or slashes.
• An option is used that the installed version of Windows does not support.

Copying commands from formatted web pages is a frequent cause, because typographic dashes are not the same as the hyphen DISM expects.

First Steps to Try

Type the command carefully.

1. Close Command Prompt, then right-click Start and choose Command Prompt (Admin) or Windows PowerShell (Admin).
2. Type the command manually rather than pasting it: DISM /Online /Cleanup-Image /RestoreHealth.
3. Make sure there is a space before each slash.
4. Press Enter and wait.
5. If it works, run sfc /scannow afterwards.

Checking each space and slash usually solves the problem immediately.

Remember that capital letters do not matter to DISM, but spaces and the exact spelling of each option do.

If the Problem Continues

Check the DISM version and options.

1. Run DISM /Online /Cleanup-Image /CheckHealth to test a simpler option.
2. Run winver to confirm your Windows 10 version supports the command you are using.
3. Restart the PC to clear pending changes.
4. If you used a /Source option, check the path and the image index are correct.
5. Run sfc /scannow to repair DISM’s own files if needed.

Protect Your Data First

DISM commands repair Windows, but mistyped commands can target the wrong image. Double-check paths before pressing Enter, especially when using a source image.

The Bottom Line

DISM error 87 usually means the command was not typed correctly. Open an administrator prompt, type commands manually with correct spacing, and confirm your Windows version supports the option.

Once DISM runs correctly, let it finish completely, even if the progress bar pauses at 20 or 40 percent for several minutes.