diff --git a/www/common/onlyoffice/inner.js b/www/common/onlyoffice/inner.js
index 7e60bcc81..66cc2382a 100644
--- a/www/common/onlyoffice/inner.js
+++ b/www/common/onlyoffice/inner.js
@@ -2171,12 +2171,52 @@ define([
                     });
                 }
 
-                if (APP.startNew) {
-                    var w = getWindow();
-                    if (lang === "fr") { lang = 'fr-fr'; }
-                    var l = w.Common.util.LanguageInfo.getLocalLanguageCode(lang);
-                    getEditor().asc_setDefaultLanguage(l);
+                //Ensure spellcheck set correctly (works only with localized language variants)
+                var editor = getEditor();
+                if (typeof editor.asc_getDefaultLanguage === 'function' && typeof editor.asc_setDefaultLanguage === 'function') {
+
+                    var defaultLanguageCode = editor.asc_getDefaultLanguage();
+
+                    const langToLocale = {
+                        "en" : "en-us",
+                        "fr" : "fr-fr",
+                        "es" : "es-es",
+                        "de" : "de-de"
+                    };
+
+                    const langCodeToLocale = {
+                        7: "de-de",
+                        9: "en-us",
+                        10: "es-es",
+                        12: "fr-fr"
+                    };
+
+                    const localeToLCID = Object.fromEntries(
+                        Object.values(window.frames[0].AscCommon.g_aCultureInfos)
+                            .map(info => [info.Name.toLowerCase(), info.LCID])
+                    );
+
+                    if (APP.startNew) {
+                        var w = getWindow();
+                        //If default language variant is generic - localize it
+                        if (Object.keys(langToLocale).includes(lang)) {
+                            lang = langToLocale[lang];
+                        }
+                        var l = w.Common.util.LanguageInfo.getLocalLanguageCode(lang);
+                        editor.asc_setDefaultLanguage(l);
+
+                    } else {
+                        //Setting the language every time document loads prevents spellcheck from 'switching off'
+                        var localeLang = langCodeToLocale[defaultLanguageCode];
+
+                        //If default language variant is generic - localize it
+                        if (defaultLanguageCode < 1000 && localeLang) {
+                            defaultLanguageCode = localeToLCID[localeLang];
+                        }
+                        editor.asc_setDefaultLanguage(defaultLanguageCode);
+                    }
                 }
+
             }
 
             sframeChan.event('EV_OO_DOC_READY');