Knowledgebase > Installation > Troubleshooting > Error: 'Unable to read expected size from installation instruction file. Instruction file needs repair'

Error: 'Unable to read expected size from installation instruction file. Instruction file needs repair'

This error message can occur when doing a full installation or installing updates for your instrument, and has multiple potential causes:

Installer File Has Been Moved

The most common cause of this error message is the moving/dragging of the installer file from within its folder (usually an installation or update folder), which breaks the connection between the installer and the data it is meant to install. 

For example, moving the "Omnisphere 2 Installer.pkg" to the Desktop, on a Mac. 

Returning the installer to its original location within the containing folder should solve this issue.

If you aren't sure how to return the installer to its original location, you can alternatively download a new installation/update folder and then run the new installer from its original location within the new folder.

External Drive Improperly Formatted or Configured for Time Machine:

If you're trying to install to an external hard drive (or if your instrument is already installed to an external hard drive), you'll first want to ensure that your external drive meets the Format Guidelines. If using a Mac, you'll also want to confirm that your external hard drive is not configured for Time Machine backups.

ZIP File Improperly Extracted:

When extracting the ZIP file for the installer or update, make sure to use your operating system's built-in extraction / archive utility. Third-party software such as WinZip, WinRAR, 7Zip, etc. has been known to improperly extract the data from the folder.

On Mac, right-click on the ZIP file and select Open With > Archive Utility.

On Windows, right-click on the ZIP file and select Open With > Windows Explorer

When the new window opens, click the Extract All button at the top of the File Explorer window to continue extracting the folder.


After extracting the folder, try running the installer application within the extracted folder.

Permissions Issues:

When running the installer or updater, you may be prompted to allow access to your Downloads/Desktop folder or Removable Volumes.


Click Allow or OK on any of these pop-up messages that you see to ensure that the installer has permission to access and install the data.

If you've accidentally clicked "Don't Allow", please move the installation or update folder to a different location, such as your Music folder, and reattempt installation.

During installation, please ensure that you select OK when prompted with the message above.

Security Software:

Security and cleaning software such as Windows Defender, Norton, McAfee, CleanMyMac, and Mackeeper can potentially affect and alter the data within the installation or update folder, so you will want to temporarily disable any of this software when attempting to install your instrument or update.

Note: Specific programs for Macs such as MacKeeper and CleanMyMac have been known to cause this error message among other issues, so we recommend uninstalling these programs from your computer using the built-in Uninstaller module in the software. If you wish to maintain an extra layer of security for your system, we recommend using Malwarebytes instead.

If you were using security software when you initially downloaded the installer or update, you'll need to redownload the installer / update after disabling the security software.

Follow the steps below when redownloading:

Full Installation w/ Download Manager: Delete the DownloadManager.dmg/exe file and relevant installation folder (Omnisphere 2 Installation, Keyscape Installation, etc.). Then you can obtain a new Download Manager using the Reinstall tab in your user account to try redownloading the installation folder.

Full Installation w/ USB Installer: Delete the relevant installation folder (Keyscape_Installation, Trilian_Installation, etc.), then redownload the installation folder after double-clicking the Installation.url file located in your USB installer

Smart Update: Delete the Spectrasonics Updater folder and ZIP file, then click the Get Updates button on your instrument's splash screen to redownload the Smart Update installer.

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