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.
In this comprehensive guide, we will explain what DISM Error 87 means, why it happens, and provide to fix it permanently. What is DISM Error 87? DISM (Deployment Imaging and Service Management) is a built-in command-line tool in Windows 10 and Windows 11. It is used to repair the Windows system image, including the recovery environment and Windows PE. dism error 87 fixed
When you type a DISM command (for example, to check health or restore health), the tool parses every space, slash, and colon. is the DISM equivalent of "I don’t understand what you just typed." It indicates that the syntax is incorrect, a parameter is misspelled, or a colon is missing. Typically displayed in the Command Prompt as Error:
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. It is almost always fixable within minutes
Open CMD as Administrator. Step 2: Type DISM /? and press Enter. This shows the full help menu. Step 3: To see syntax for specific operations, use:
Missing colon after Online .
DISM /Online /Cleanup-Image /RestoreHealth Result: Error: 87 – The option is unknown.