diff --git a/plugins/e57/libE57Format/src/E57Exception.cpp b/plugins/e57/libE57Format/src/E57Exception.cpp
index 2267920e9b..06e03d8bd7 100644
--- a/plugins/e57/libE57Format/src/E57Exception.cpp
+++ b/plugins/e57/libE57Format/src/E57Exception.cpp
@@ -366,6 +366,6 @@ namespace e57
          case E57_ERROR_INVARIANCE_VIOLATION:
             return "class invariance constraint violation in debug mode (E57_ERROR_INVARIANCE_VIOLATION)";
       }
+      return "Unknown error.";
    }
-
 }