diff --git a/src/providers/lang.ts b/src/providers/lang.ts
index a4821245d..363a245cd 100644
--- a/src/providers/lang.ts
+++ b/src/providers/lang.ts
@@ -173,7 +173,7 @@ export class CoreLangProvider {
             return language;
         }).catch(() => {
             // User hasn't defined a language. If default language is forced, use it.
-            if (CoreConfigConstants.default_lang && !CoreConfigConstants.forcedefaultlanguage) {
+            if (CoreConfigConstants.default_lang && CoreConfigConstants.forcedefaultlanguage) {
                 return CoreConfigConstants.default_lang;
             }
 
@@ -190,6 +190,11 @@ export class CoreLangProvider {
                         }
                     }
 
+                    if (typeof CoreConfigConstants.languages[language] == 'undefined') {
+                        // Language not supported, use fallback language.
+                        return this.fallbackLanguage;
+                    }
+
                     return language;
                 }).catch(() => {
                     // Error getting locale. Use default language.