diff --git a/src/main/java/sirius/kernel/async/CallContext.java b/src/main/java/sirius/kernel/async/CallContext.java
index 6809cad4..1846f650 100644
--- a/src/main/java/sirius/kernel/async/CallContext.java
+++ b/src/main/java/sirius/kernel/async/CallContext.java
@@ -9,6 +9,7 @@
 package sirius.kernel.async;
 
 import sirius.kernel.Sirius;
+import sirius.kernel.commons.Explain;
 import sirius.kernel.commons.Strings;
 import sirius.kernel.commons.Tuple;
 import sirius.kernel.commons.Value;
@@ -359,6 +360,8 @@ public <C extends SubContext> void set(Class<C> contextType, C instance) {
      *
      * @return a two-letter language code used for the current thread.
      */
+    @SuppressWarnings("deprecation")
+    @Explain("The replacement for NLS.getDefaultLanguage() is only available in sirius-web.")
     public String getLang() {
         if (lang == null) {
             invokeLazyLanguageInstaller();
diff --git a/src/main/java/sirius/kernel/nls/NLS.java b/src/main/java/sirius/kernel/nls/NLS.java
index 58fa6a01..6b9038ac 100644
--- a/src/main/java/sirius/kernel/nls/NLS.java
+++ b/src/main/java/sirius/kernel/nls/NLS.java
@@ -131,6 +131,7 @@ public static String getCurrentLang() {
      * @return the language code of the default language
      */
     @Nonnull
+    @Deprecated
     public static String getDefaultLanguage() {
         if (defaultLanguage != null) {
             return defaultLanguage;