| Cause | Explanation | | :--- | :--- | | | Missing spaces, extra slashes, or misspelled words (e.g., Ckeanup instead of Cleanup ). | | Missing colons | Forgetting the colon after Online ( /Online: is required, not just /Online ). | | Wrong slashes | Using backslashes ( \ ) instead of forward slashes ( / ). | | Incorrect command order | DISM is sensitive to the sequence of arguments. | | Corrupt DISM binary | Rare, but possible if system files are damaged. |
Now that you know how to fix DISM Error 87, you can return to repairing your Windows image and keeping your PC healthy. Do you have a specific DISM command that still triggers Error 87? Check the official Microsoft documentation for DISM syntax or leave a comment below for a tailored fix. dism error 87 fixed
By carefully reviewing your command, ensuring /Online: has the colon, and running the tool with administrative privileges, you will resolve this error in under two minutes. For the rare cases where the error persists, repairing your system files with SFC or switching to PowerShell will get the job done. | Cause | Explanation | | :--- |
Typically displayed in the Command Prompt as Error: 87 – The option is unknown , this error halts your repair efforts immediately. While the message sounds vague, it is actually a very specific syntax error. The good news? It is almost always fixable within minutes. | | Incorrect command order | DISM is
If you are copying commands from a website, paste them into Notepad first and look for auto‑formatted slashes. If you are unsure about a specific DISM switch, let DISM teach you the correct format.
DISM /Online /Cleanup-Image /RestoreHealth Result: Error: 87 – The option is unknown.
Let’s fix it. In 90% of cases, Error 87 is caused by a missing colon after Online . Many old tutorials omit the colon, but modern Windows versions require it strictly.