diff --git a/src/guiguts/application.py b/src/guiguts/application.py
index 8e7f478a..422d8424 100644
--- a/src/guiguts/application.py
+++ b/src/guiguts/application.py
@@ -894,7 +894,9 @@ def selection_str() -> str:
         )
 
         the_statusbar.add(
-            "languages label", tooltip="Click: Set language(s)", text="Lang: "
+            "languages label",
+            tooltip="Click: Set language(s), e.g. 'en' or 'de fr'",
+            text="Lang: ",
         )
         the_statusbar.add_binding(
             "languages label", "ButtonRelease-1", self.file.set_languages
diff --git a/src/guiguts/file.py b/src/guiguts/file.py
index 9414ed86..076507e2 100644
--- a/src/guiguts/file.py
+++ b/src/guiguts/file.py
@@ -114,6 +114,7 @@ def __init__(
         self._filename_callback = filename_callback
         self._image_dir = ""
         self._project_id = ""
+        self._languages = "en"
         self._languages_callback = languages_callback
         self.page_details = PageDetails()
         self.project_dict = ProjectDict()
@@ -178,13 +179,17 @@ def languages(self) -> Any:
 
     @languages.setter
     def languages(self, value: str) -> None:
+        value = value.strip()
         if not value:
-            value = "en"
+            value = self._languages if self._languages else "en"
+        if re.fullmatch(r"[a-z_]+(\+[a-z_]+)*", value) is None:
+            logger.error("Invalid language code(s): valid examples are 'en' or 'de fr'")
+            return
         self._languages = value
         self._languages_callback()
-        preferences.set(PrefKey.DEFAULT_LANGUAGES, value)
+        preferences.set(PrefKey.DEFAULT_LANGUAGES, self._languages)
         # Inform maintext, so text manipulation algorithms there can check languages
-        maintext().set_languages(value)
+        maintext().set_languages(self._languages)
 
     def reset(self) -> None:
         """Reset file internals to defaults, e.g. filename, page markers, etc.
diff --git a/src/guiguts/maintext.py b/src/guiguts/maintext.py
index 3b606e2d..60b802a9 100644
--- a/src/guiguts/maintext.py
+++ b/src/guiguts/maintext.py
@@ -1926,11 +1926,10 @@ def capitalize_first_letter(match: re.regex.Match[str]) -> str:
     def set_languages(self, languages: str) -> None:
         """Set languages used in text.
 
-        Multiple languages are separated by "+"
+        Args:
+            languages: Language, or list of languages separated by "+". Assumed valid.
         """
-        if languages:
-            assert re.match(r"[a-z_]+(\+[a-z_]+)*", languages)
-            self.languages = languages
+        self.languages = languages
 
     def get_language_list(self) -> list[str]:
         """Get list of languages used in text.