diff --git a/setup/translations.py b/setup/translations.py
index 714d4c7c90..426972dc8d 100644
--- a/setup/translations.py
+++ b/setup/translations.py
@@ -294,7 +294,8 @@ class Translations(POT):  # {{{
             base = os.path.dirname(dest)
             if not os.path.exists(base):
                 os.makedirs(base)
-            data, current_hash = self.hash_and_data(src)
+            data, h = self.hash_and_data(src)
+            current_hash = h.digest()
             saved_hash, saved_data = self.read_cache(src)
             if current_hash == saved_hash:
                 with open(dest, 'wb') as d:
@@ -384,7 +385,7 @@ class Translations(POT):  # {{{
             data = s.read()
         h = hashlib.sha1(data)
         h.update(f.encode('utf-8'))
-        return data, h.digest()
+        return data, h
 
     def compile_content_server_translations(self):
         self.info('Compiling content-server translations')
@@ -392,7 +393,8 @@ class Translations(POT):  # {{{
         from calibre.utils.zipfile import ZipFile, ZIP_DEFLATED, ZipInfo, ZIP_STORED
         with ZipFile(self.j(self.RESOURCES, 'content-server', 'locales.zip'), 'w', ZIP_DEFLATED) as zf:
             for src in glob.glob(os.path.join(self.TRANSLATIONS, 'content-server', '*.po')):
-                data, current_hash = self.hash_and_data(src)
+                data, h = self.hash_and_data(src)
+                current_hash = h.digest()
                 saved_hash, saved_data = self.read_cache(src)
                 if current_hash == saved_hash:
                     raw = saved_data
@@ -402,7 +404,8 @@ class Translations(POT):  # {{{
                     po_data = data.decode('utf-8')
                     data = json.loads(msgfmt(po_data))
                     translated_entries = {k:v for k, v in data['entries'].iteritems() if v and sum(map(len, v))}
-                    data['entries'] = translated_entries
+                    data[u'entries'] = translated_entries
+                    data[u'hash'] = h.hexdigest()
                     cdata = b'{}'
                     if translated_entries:
                         raw = json.dumps(data, ensure_ascii=False, sort_keys=True)
diff --git a/src/calibre/srv/code.py b/src/calibre/srv/code.py
index d4c2b024e3..1f77ebaaba 100644
--- a/src/calibre/srv/code.py
+++ b/src/calibre/srv/code.py
@@ -154,12 +154,16 @@ def basic_interface_data(ctx, rd):
     return ans
 
 
-@endpoint('/interface-data/update', postprocess=json)
-def update_interface_data(ctx, rd):
+@endpoint('/interface-data/update/{translations_hash=None}', postprocess=json)
+def update_interface_data(ctx, rd, translations_hash):
     '''
     Return the interface data needed for the server UI
     '''
-    return basic_interface_data(ctx, rd)
+    ans = basic_interface_data(ctx, rd)
+    t = ans['translations']
+    if t and (t.get('hash') or translations_hash) and t.get('hash') == translations_hash:
+        del ans['translations']
+    return ans
 
 
 def get_field_list(db):
diff --git a/src/pyj/book_list/main.pyj b/src/pyj/book_list/main.pyj
index 6c38801908..eaae90ae92 100644
--- a/src/pyj/book_list/main.pyj
+++ b/src/pyj/book_list/main.pyj
@@ -122,7 +122,12 @@ def load_interface_data():
 
 
 def do_update_interface_data():
-    ajax('interface-data/update', def (end_type, xhr, ev):
+    t = get_translations()
+    thash = t?.hash
+    url = 'interface-data/update'
+    if thash:
+        url += '/' + thash
+    ajax(url, def (end_type, xhr, ev):
         if end_type is 'load':
             data = JSON.parse(xhr.responseText)
             update_interface_data(data)