diff --git a/CHANGELOG.md b/CHANGELOG.md
index 68ab8af00..c16148f29 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,9 +3,11 @@
 ### `@krassowski/jupyterlab-lsp 3.7.1` (unreleased)
 
 - bug fixes:
-  - fix rename shortcut registration in file browser ([#614])
+  - fix rename shortcut registration in file editor ([#614])
+  - add a note on manually enabling backend extension ([#621], thanks @icankeep)
 
 [#614]: https://github.com/krassowski/jupyterlab-lsp/pull/614
+[#621]: https://github.com/krassowski/jupyterlab-lsp/pull/621
 
 ### `jupyter-lsp 1.3.0` (2021-06-02)
 
diff --git a/packages/jupyterlab-lsp/src/errors.tsx b/packages/jupyterlab-lsp/src/errors.tsx
index 34b739a04..2e10c89cd 100644
--- a/packages/jupyterlab-lsp/src/errors.tsx
+++ b/packages/jupyterlab-lsp/src/errors.tsx
@@ -50,7 +50,9 @@ export const SERVER_EXTENSION_404 = (
     <p>
       Please ensure that <code>jupyter server extension list</code> includes
       jupyter-lsp and that it is enabled. If it is enabled please try to restart
-      JupyterLab.
+      JupyterLab. If the server extension is installed but not enabled and all
+      other suggestions listed above failed try the following:
+      <code>jupyter server extension enable --user --py jupyter_lsp</code>
     </p>
   </div>
 );
diff --git a/requirements/dev.txt b/requirements/dev.txt
index 966a8e863..0caa297b2 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -8,3 +8,4 @@ pytest-cov
 ruamel.yaml
 robotframework-lint >=1.1
 robotframework >=3.2
+types-six
diff --git a/requirements/lint.yml b/requirements/lint.yml
index 283cb8d8b..4b8439069 100644
--- a/requirements/lint.yml
+++ b/requirements/lint.yml
@@ -5,9 +5,12 @@ channels:
   - nodefaults
 
 dependencies:
+  - pip
   - black
   - isort
   - mypy
   - robotframework-lint >=1.1
   - robotframework >=4
   - pytest-tornasync
+  - pip:
+      - types-six