diff --git a/legacy/elementary/src/lib/elm_config.c b/legacy/elementary/src/lib/elm_config.c
index 3e273cc990..26e406c967 100644
--- a/legacy/elementary/src/lib/elm_config.c
+++ b/legacy/elementary/src/lib/elm_config.c
@@ -1205,6 +1205,8 @@ _env_get(void)
           eina_stringshare_replace(&_elm_config->engine, ELM_WAYLAND_SHM);
         else if ((!strcasecmp(s, "wayland_egl")))
           eina_stringshare_replace(&_elm_config->engine, ELM_WAYLAND_EGL);
+        else
+          ERR("Unknown engine '%s'.", s);
      }
 
    s = getenv("ELM_VSYNC");