diff --git a/sphinx/builders/html/__init__.py b/sphinx/builders/html/__init__.py
index f5152f6da3a..1dbde6e371e 100644
--- a/sphinx/builders/html/__init__.py
+++ b/sphinx/builders/html/__init__.py
@@ -754,9 +754,13 @@ def copy_translation_js(self) -> None:
     def copy_stemmer_js(self) -> None:
         """Copy a JavaScript file for stemmer."""
         if self.indexer is not None:
-            jsfile = self.indexer.get_js_stemmer_rawcode()
-            if jsfile:
-                copyfile(jsfile, path.join(self.outdir, '_static', '_stemmer.js'))
+            if hasattr(self.indexer, 'get_js_stemmer_rawcodes'):
+                for jsfile in self.indexer.get_js_stemmer_rawcodes():
+                    copyfile(jsfile, path.join(self.outdir, '_static', path.basename(jsfile)))
+            else:
+                jsfile = self.indexer.get_js_stemmer_rawcode()
+                if jsfile:
+                    copyfile(jsfile, path.join(self.outdir, '_static', '_stemmer.js'))
 
     def copy_theme_static_files(self, context: Dict) -> None:
         def onerror(filename: str, error: Exception) -> None:
diff --git a/sphinx/search/__init__.py b/sphinx/search/__init__.py
index 6c748aed19f..cd099a6b5c1 100644
--- a/sphinx/search/__init__.py
+++ b/sphinx/search/__init__.py
@@ -439,15 +439,34 @@ def context_for_searchtool(self) -> Dict[str, Any]:
             js_splitter_code = self.js_splitter_code
 
         return {
-            'search_language_stemming_code': self.lang.js_stemmer_code,
+            'search_language_stemming_code': self.get_js_stemmer_code(),
             'search_language_stop_words': jsdump.dumps(sorted(self.lang.stopwords)),
             'search_scorer_tool': self.js_scorer_code,
             'search_word_splitter_code': js_splitter_code,
         }
 
+    def get_js_stemmer_rawcodes(self) -> List[str]:
+        """Returns a list of non-minified stemmer JS files to copy."""
+        if self.lang.js_stemmer_rawcode:
+            return [
+                path.join(package_dir, 'search', 'non-minified-js', fname)
+                for fname in ('base-stemmer.js', self.lang.js_stemmer_rawcode)
+            ]
+        else:
+            return []
+
     def get_js_stemmer_rawcode(self) -> str:
+        return None
+
+    def get_js_stemmer_code(self) -> str:
+        """Returns JS code that will be inserted into language_data.js."""
         if self.lang.js_stemmer_rawcode:
-            return path.join(package_dir, 'search', 'non-minified-js',
-                             self.lang.js_stemmer_rawcode)
+            js_dir = path.join(package_dir, 'search', 'minified-js')
+            with open(path.join(js_dir, 'base-stemmer.js')) as js_file:
+                base_js = js_file.read()
+            with open(path.join(js_dir, self.lang.js_stemmer_rawcode)) as js_file:
+                language_js = js_file.read()
+            return ('%s\n%s\nStemmer = %sStemmer;' %
+                    (base_js, language_js, self.lang.language_name))
         else:
-            return None
+            return self.lang.js_stemmer_code