diff --git a/swh/web/common/highlightjs.py b/swh/web/common/highlightjs.py
index 54661d62..d2386e19 100644
--- a/swh/web/common/highlightjs.py
+++ b/swh/web/common/highlightjs.py
@@ -1,154 +1,164 @@
 # Copyright (C) 2017-2019  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU Affero General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import functools
 import json
 from typing import Dict
 
 from pygments.lexers import get_all_lexers, get_lexer_for_filename
 import sentry_sdk
 
 from django.contrib.staticfiles.finders import find
 
-with open(str(find("json/highlightjs-languages.json")), "r") as _hljs_languages_file:
-    _hljs_languages_data = json.load(_hljs_languages_file)
+
+@functools.lru_cache()
+def _hljs_languages_data():
+    with open(str(find("json/highlightjs-languages.json")), "r") as hljs_languages_file:
+        return json.load(hljs_languages_file)
+
 
 # set of languages ids that can be highlighted by highlight.js library
-_hljs_languages = set(_hljs_languages_data["languages"])
+@functools.lru_cache()
+def _hljs_languages():
+    return set(_hljs_languages_data()["languages"])
+
 
 # languages aliases defined in highlight.js
-_hljs_languages_aliases = {
-    **_hljs_languages_data["languages_aliases"],
-    "ml": "ocaml",
-    "bsl": "1c",
-    "ep": "mojolicious",
-    "lc": "livecode",
-    "p": "parser3",
-    "pde": "processing",
-    "rsc": "routeros",
-    "s": "armasm",
-    "sl": "rsl",
-}
+@functools.lru_cache()
+def _hljs_languages_aliases():
+    return {
+        **_hljs_languages_data()["languages_aliases"],
+        "ml": "ocaml",
+        "bsl": "1c",
+        "ep": "mojolicious",
+        "lc": "livecode",
+        "p": "parser3",
+        "pde": "processing",
+        "rsc": "routeros",
+        "s": "armasm",
+        "sl": "rsl",
+    }
+
 
 # dictionary mapping pygment lexers to hljs languages
 _pygments_lexer_to_hljs_language = {}  # type: Dict[str, str]
 
 
 # dictionary mapping mime types to hljs languages
 _mime_type_to_hljs_language = {
     "text/x-c": "c",
     "text/x-c++": "cpp",
     "text/x-msdos-batch": "dos",
     "text/x-lisp": "lisp",
     "text/x-shellscript": "bash",
 }
 
 # dictionary mapping filenames to hljs languages
 _filename_to_hljs_language = {
     "cmakelists.txt": "cmake",
     ".htaccess": "apache",
     "httpd.conf": "apache",
     "access.log": "accesslog",
     "nginx.log": "accesslog",
     "resolv.conf": "dns",
     "dockerfile": "docker",
     "nginx.conf": "nginx",
     "pf.conf": "pf",
 }
 
 
 # function to fill the above dictionaries
 def _init_pygments_to_hljs_map():
     if len(_pygments_lexer_to_hljs_language) == 0:
         for lexer in get_all_lexers():
             lexer_name = lexer[0]
             lang_aliases = lexer[1]
             lang_mime_types = lexer[3]
             lang = None
             for lang_alias in lang_aliases:
-                if lang_alias in _hljs_languages:
+                if lang_alias in _hljs_languages():
                     lang = lang_alias
                     _pygments_lexer_to_hljs_language[lexer_name] = lang_alias
                     break
 
             if lang:
                 for lang_mime_type in lang_mime_types:
                     if lang_mime_type not in _mime_type_to_hljs_language:
                         _mime_type_to_hljs_language[lang_mime_type] = lang
 
 
 def get_hljs_language_from_filename(filename):
     """Function that tries to associate a language supported by highlight.js
     from a filename.
 
     Args:
         filename: input filename
 
     Returns:
         highlight.js language id or None if no correspondence has been found
     """
     _init_pygments_to_hljs_map()
     if filename:
         filename_lower = filename.lower()
         if filename_lower in _filename_to_hljs_language:
             return _filename_to_hljs_language[filename_lower]
-        if filename_lower in _hljs_languages:
+        if filename_lower in _hljs_languages():
             return filename_lower
         exts = filename_lower.split(".")
         # check if file extension matches an hljs language
         # also handle .ext.in cases
         for ext in reversed(exts[-2:]):
-            if ext in _hljs_languages:
+            if ext in _hljs_languages():
                 return ext
-            if ext in _hljs_languages_aliases:
-                return _hljs_languages_aliases[ext]
+            if ext in _hljs_languages_aliases():
+                return _hljs_languages_aliases()[ext]
 
         # otherwise use Pygments language database
         lexer = None
         # try to find a Pygment lexer
         try:
             lexer = get_lexer_for_filename(filename)
         except Exception as exc:
             sentry_sdk.capture_exception(exc)
         # if there is a correspondence between the lexer and an hljs
         # language, return it
         if lexer and lexer.name in _pygments_lexer_to_hljs_language:
             return _pygments_lexer_to_hljs_language[lexer.name]
         # otherwise, try to find a match between the file extensions
         # associated to the lexer and the hljs language aliases
         if lexer:
             exts = [ext.replace("*.", "") for ext in lexer.filenames]
             for ext in exts:
-                if ext in _hljs_languages_aliases:
-                    return _hljs_languages_aliases[ext]
+                if ext in _hljs_languages_aliases():
+                    return _hljs_languages_aliases()[ext]
     return None
 
 
 def get_hljs_language_from_mime_type(mime_type):
     """Function that tries to associate a language supported by highlight.js
     from a mime type.
 
     Args:
         mime_type: input mime type
 
     Returns:
         highlight.js language id or None if no correspondence has been found
     """
     _init_pygments_to_hljs_map()
     if mime_type and mime_type in _mime_type_to_hljs_language:
         return _mime_type_to_hljs_language[mime_type]
     return None
 
 
 @functools.lru_cache()
 def get_supported_languages():
     """
     Return the list of programming languages that can be highlighted using the
     highlight.js library.
 
     Returns:
         List[str]: the list of supported languages
     """
-    return sorted(list(_hljs_languages))
+    return sorted(list(_hljs_languages()))