diff --git a/qutebrowser/browser/webengine/spell.py b/qutebrowser/browser/webengine/spell.py
index 66c87f2a5..99595160c 100644
--- a/qutebrowser/browser/webengine/spell.py
+++ b/qutebrowser/browser/webengine/spell.py
@@ -79,7 +79,7 @@ class Language:
 def get_dictionary_dir():
     """Return the path to the QtWebEngine's dictionaries directory."""
     return os.path.join(QLibraryInfo.location(QLibraryInfo.DataPath),
-                        '/qtwebengine_dictionaries')
+                        'qtwebengine_dictionaries')
 
 
 def get_language_list_file():
diff --git a/qutebrowser/browser/webengine/webenginesettings.py b/qutebrowser/browser/webengine/webenginesettings.py
index 1ee017660..9124fec06 100644
--- a/qutebrowser/browser/webengine/webenginesettings.py
+++ b/qutebrowser/browser/webengine/webenginesettings.py
@@ -140,9 +140,16 @@ class DictionaryLanguageSetter(DefaultProfileSetter):
         if settings is not None:
             raise ValueError("'settings' may not be set with "
                              "DictionaryLanguageSetter!")
-        files = [lang.file[:-5]
-                 for lang in get_installed_languages() if lang.code in value]
-        super()._set(files, settings)
+        installed_langs = dict([(lang.code, lang.file)
+                                for lang in get_installed_languages()])
+        lang_files = []
+        for lang_code in value:
+            if lang_code in installed_langs:
+                lang_files.append(installed_langs[lang_code][:-5])
+            else:
+                message.warning('Language {} is not installed.'
+                                .format(lang_code))
+        super()._set(lang_files, settings)
 
 
 def _init_stylesheet(profile):