diff --git a/.github/workflows/tox.yml b/.github/workflows/tox.yml
index 0e25a42080..0ec1e1f0df 100644
--- a/.github/workflows/tox.yml
+++ b/.github/workflows/tox.yml
@@ -99,6 +99,16 @@ jobs:
       - name: Install Python dependencies
         run: |
           python -m pip install -r requirements/project.txt
+      - name: Check if the locales are supported by lunr.js
+        run: |
+          for locale in $(ls mkdocs/themes/mkdocs/locales/); do
+            if [[ "${locale}" != "en" ]]; then
+              if [[ ! -f "mkdocs/contrib/search/lunr-language/lunr.${locale}.js" ]]; then
+                echo "WARNING: locale '${locale}' is not supported by lunr.js"
+              fi
+            fi
+          done
+        shell: bash
       - name: Check if Portable Object Templates should have been updated
         run: |
           python setup.py extract_messages -t mkdocs
diff --git a/mkdocs/contrib/search/__init__.py b/mkdocs/contrib/search/__init__.py
index 1ca09863e0..0379cb6384 100644
--- a/mkdocs/contrib/search/__init__.py
+++ b/mkdocs/contrib/search/__init__.py
@@ -22,11 +22,12 @@ def run_validation(self, value):
             value = [value]
         elif not isinstance(value, (list, tuple)):
             raise config_options.ValidationError('Expected a list of language codes.')
-        for lang in value:
+        for lang in list(value):
             if lang != 'en' and not self.lang_file_exists(lang):
-                raise config_options.ValidationError(
-                    f'"{lang}" is not a supported language code.'
+                log.warning(
+                    f'Ignoring search.lang "{lang}" as it is not a supported language code.'
                 )
+                value.remove(lang)
         return value