diff --git a/src/ceev.cc b/src/ceev.cc
index ebc99b8..09793d9 100644
--- a/src/ceev.cc
+++ b/src/ceev.cc
@@ -213,8 +213,10 @@ int devel(std::deque<std::string> args) {
     return devel_roadmap();
   if (a1 == "sdl2")
     return devel_sdl2(args);
-  if (a1 == "lang")
+  if (a1 == "lang") {
+    std::cerr << "Not implemented" << std::endl;
     return 1;
+  }
 
   std::string kw;
   if (a1.substr(0, 2) == "--") {