diff --git a/changelog.d/1118.improvements b/changelog.d/1118.improvements
new file mode 100644
index 0000000000..90478180df
--- /dev/null
+++ b/changelog.d/1118.improvements
@@ -0,0 +1 @@
+Améliorer l'explication pour un externe voulant rejoindre un salon sans autorisation.
\ No newline at end of file
diff --git a/vector/src/main/java/im/vector/app/core/error/ErrorFormatter.kt b/vector/src/main/java/im/vector/app/core/error/ErrorFormatter.kt
index 47e650b41b..5cf32fad97 100644
--- a/vector/src/main/java/im/vector/app/core/error/ErrorFormatter.kt
+++ b/vector/src/main/java/im/vector/app/core/error/ErrorFormatter.kt
@@ -123,7 +123,8 @@ class DefaultErrorFormatter @Inject constructor(
                     throwable.error.code == MatrixError.M_PASSWORD_NO_SYMBOL -> {
                         stringProvider.getString(CommonStrings.tchap_register_pwd_no_symbol)
                     }
-                    throwable.error.code == MatrixError.M_UNKNOWN &&
+                    // TCHAP Add explicit error when a user is not allowed to access a room.
+                    (throwable.error.code == MatrixError.M_UNKNOWN || throwable.error.code == MatrixError.M_FORBIDDEN) &&
                             throwable.error.message == "Not allowed to join this room" -> {
                         stringProvider.getString(CommonStrings.room_error_access_unauthorized)
                     }