---
title: "Fix error 1001 during Document Converter upgrade"
canonical_url: "https://www.nutrient.io/guides/document-converter/sharepoint/troubleshooting/error-1001-an-exception-occurred-in-the-onafterinstall-event-handler-during-upgrade/"
md_url: "https://www.nutrient.io/guides/document-converter/sharepoint/troubleshooting/error-1001-an-exception-occurred-in-the-onafterinstall-event-handler-during-upgrade.md"
last_updated: "2026-06-08T15:36:24.927Z"
description: "Learn to resolve error 1001 during the upgrade of Document Converter for SharePoint to ensure a smooth installation process."
---

# Troubleshooting error 1001 in SharePoint upgrades

_**Please note that the following only applies to versions of the Document Converter older than 8.0. The most recent release comes with a [new installer](https://www.nutrient.io/blog/muhimbi-pdf-converter-new-setup-experience/).**_

When upgrading the Document Converter for SharePoint from an old version you may receive an error similar to the following:

> Error 1001. An exception occurred in the OnAfterInstall event handler

This error may happen if the upgrade sequence in the Administration Guide is not followed. It is essential that the  old front end WSP is uninstalled before the new service is installed. Otherwise old DLLs may be picked up from the Global Assembly Cache.

If you are receiving this error even though the WSP has been uninstalled then another process may keep the DLLs locked. Solve this as follows:

1. Uninstall the front end WSP using uninstall.cmd.

2. Navigate your file explorer to %windir%\assembly.

3. Sort by name and scroll to Muhimbi.*

4. Select any Muhimbi entries with version 1.0.1.1 (Do not select any other Muhimbi related entries)

5. Press the delete key.

6. Run setup.exe again.

---

## Related pages

- [Converting IRM and DRM protected documents seamlessly](/guides/document-converter/sharepoint/troubleshooting/dealing-with-the-conversion-of-irm-drm-rms-aip-protected-documents.md)
- [CabLib Extract ERROR when converting InfoPath files](/guides/document-converter/sharepoint/troubleshooting/cablib-extract-error-when-converting-infopath-files.md)
- [Converting HTML - Empty page / Authentication problems](/guides/document-converter/sharepoint/troubleshooting/converting-html-web-pages-returns-an-empty-pdf.md)
- [Debugging Web Service calls and Soap Messages](/guides/document-converter/sharepoint/troubleshooting/debugging-web-service-calls-and-soap-messages.md)
- [How to check if a SharePoint server runs workflows](/guides/document-converter/sharepoint/troubleshooting/determining-if-a-server-is-involved-in-executing-workflows.md)
- [How to Disable Incremental Updates When Watermarking?](/guides/document-converter/sharepoint/troubleshooting/disable-incremental-update-when-watermarking.md)
- [Enable Custom App Authentication](/guides/document-converter/sharepoint/troubleshooting/enable-custom-app-authentication.md)
- [Troubleshoot PDF merging issues and solutions](/guides/document-converter/sharepoint/troubleshooting/error-while-merging-existing-pdf-files-e-g-pdflexer-errors.md)
- [Adjusting document file size limits easily](/guides/document-converter/sharepoint/troubleshooting/how-can-i-change-the-maximum-file-size-of-documents-to-process.md)
- [How do I enable debug logging?](/guides/document-converter/sharepoint/troubleshooting/how-do-i-enable-debug-logging.md)
- [Differences between SharePoint Online and on-premises Document Converter](/guides/document-converter/sharepoint/troubleshooting/how-does-the-pdf-converter-for-sharepoint-online-differ-from-the-on-premise-product.md)
- [How do I manually remove the Conversion Service?](/guides/document-converter/sharepoint/troubleshooting/how-do-i-manually-remove-the-conversion-service.md)
- [Troubleshooting: SharePoint Document Converter](/guides/document-converter/sharepoint/troubleshooting.md)
- [Check your Document Converter version easily](/guides/document-converter/sharepoint/troubleshooting/how-to-determine-which-version-of-the-pdf-converter-is-installed.md)
- [Troubleshooting InfoPath view-related errors](/guides/document-converter/sharepoint/troubleshooting/infopath-cannot-execute-any-view-related-object-model-calls-the-view-is-not-ready.md)
- [Understanding InfoPath document conversion processes](/guides/document-converter/sharepoint/troubleshooting/infopath-rules-custom-code-data-connections-are-not-executed.md)
- [Troubleshooting InfoPath form conversion issues](/guides/document-converter/sharepoint/troubleshooting/my-infopath-form-fails-to-convert-how-can-i-troubleshoot-this.md)
- [Invalid digital signature during installation](/guides/document-converter/sharepoint/troubleshooting/invalid-digital-signature-during-installation.md)
- [Troubleshooting PDF workflow issues in SharePoint](/guides/document-converter/sharepoint/troubleshooting/pdf-workflow-activities-are-not-displayed-in-sharepoint-designer-2013.md)
- [Troubleshooting Document Converter login issues](/guides/document-converter/sharepoint/troubleshooting/problems-logging-in-to-pdf-converter-services-online.md)
- [Fixing SharePoint search for HTML-to-PDF conversion](/guides/document-converter/sharepoint/troubleshooting/sharepoint-search-does-not-return-converted-html-content.md)
- [Troubleshooting SharePoint Document Converter issues](/guides/document-converter/sharepoint/troubleshooting/sharepoint-behaves-unexpectedly-after-deploying-the-pdf-converter-for-sharepoint.md)
- [Document Converter front-end WSP is stuck on 'Deploying](/guides/document-converter/sharepoint/troubleshooting/pdf-converter-front-end-wsp-is-stuck-on-deploying.md)
- [Solving formatting issues when converting HTML to PDF](/guides/document-converter/sharepoint/troubleshooting/solving-formatting-issues-when-converting-html-to-pdf.md)
- [Troubleshoot SharePoint Designer workflow issues](/guides/document-converter/sharepoint/troubleshooting/sharepoint-designer-workflow-activities-are-not-inserted.md)
- [Troubleshooting SharePoint Online menu visibility issues](/guides/document-converter/sharepoint/troubleshooting/some-menu-options-are-not-displayed-in-sharepoint-online.md)
- [The Conversion Service does not start](/guides/document-converter/sharepoint/troubleshooting/the-conversion-service-does-not-start.md)
- [Troubleshooting SharePoint document converter issues](/guides/document-converter/sharepoint/troubleshooting/troubleshooting-connectivity-problems-between-web-front-end-and-conversion-servers.md)
- [Troubleshooting install.cmd errors](/guides/document-converter/sharepoint/troubleshooting/troubleshooting-install-cmd-errors.md)
- [Troubleshooting document converter issues on SharePoint](/guides/document-converter/sharepoint/troubleshooting/troubleshooting-the-pdf-converter-for-sharepoint-online.md)
- [Using the diagnostics tool to troubleshoot conversions](/guides/document-converter/sharepoint/troubleshooting/using-the-diagnostics-tool-to-troubleshoot-conversions.md)
- [Troubleshoot evaluation message in SharePoint](/guides/document-converter/sharepoint/troubleshooting/the-license-has-been-installed-but-an-evaluation-message-is-still-displayed.md)
- [Validating converters and troubleshooting errors](/guides/document-converter/sharepoint/troubleshooting/validating-converters-and-troubleshooting-errors.md)
- [Tips for pixel-perfect InfoPath-to-PDF conversion](/guides/document-converter/sharepoint/troubleshooting/when-converting-infopath-to-pdf-my-file-does-not-look-100-the-same.md)
- [Watermarker fails to load because Microsoft now enforces Content Security Policy (CSP)](/guides/document-converter/sharepoint/troubleshooting/watermarker-blocked-by-microsoft-csp.md)
- [Convert InfoPath forms to Word and Excel easily](/guides/document-converter/sharepoint/troubleshooting/when-converting-infopath-to-word-excel-my-file-does-not-look-100-the-same.md)
- [Find the Document Converter administration screen](/guides/document-converter/sharepoint/troubleshooting/where-is-the-pdf-converter-s-central-administration-screen-located.md)
- [Where can I enable Web Application Scoped SharePoint Features?](/guides/document-converter/sharepoint/troubleshooting/where-can-i-enable-web-application-scoped-sharepoint-features.md)
- [Why are my watermarks not visible?](/guides/document-converter/sharepoint/troubleshooting/why-are-my-watermarks-not-visible.md)
- [Why are my legacy DOC and XLS files failing to convert?](/guides/document-converter/sharepoint/troubleshooting/why-are-my-legacy-doc-and-xls-files-failing-to-convert.md)
- [Understanding duplicate PDF conversion options in SharePoint](/guides/document-converter/sharepoint/troubleshooting/why-are-the-various-pdf-conversion-options-displayed-twice-in-sharepoint.md)