Notice the colon after Online ? That tiny punctuation mark is critical. Apply this to any DISM command:
It didn't error out immediately. It was working.
To fully patch system errors on Windows 7, rely primarily on the sfc /scannow command or download the official System Update Readiness Tool from Microsoft. Summary of Success dism error 87 fixed
is rarely a sign of deep system corruption. In the vast majority of cases, it is simply a syntax error caused by a missing colon, a misplaced space, or the wrong slash type.
For some users, using the System File Checker to resolve underlying corruption can clear the path for DISM to work correctly. Notice the colon after Online
If this fails with Error 87, your DISM is too old.
A broken update service preventing online image repairs. How to Fix DISM Error 87 It was working
Once you have fixed the error, follow these best practices to ensure it never returns.
The Windows Update or DISM-related background services are disabled. How to Fix DISM Error 87 (Step-by-Step)