diff --git a/compiler/cpp/src/thrift/generate/t_generator.cc b/compiler/cpp/src/thrift/generate/t_generator.cc
index f4b7150..3059fb1 100644
--- a/compiler/cpp/src/thrift/generate/t_generator.cc
+++ b/compiler/cpp/src/thrift/generate/t_generator.cc
@@ -234,6 +234,13 @@
   gen_map_t& the_map = get_generator_map();
   gen_map_t::iterator iter = the_map.find(language);
 
+  if ((language == "csharp") || (language == "netcore")) {
+    failure("The '%s' target is no longer available. Use 'netstd' instead.", language.c_str());
+  }
+  else if (language == "as3") {
+    pwarning(1, "The '%s' target is deprecated and will be removed in future Thrift versions.", language.c_str());
+  }
+
   if (iter == the_map.end()) {
     return nullptr;
   }
diff --git a/compiler/cpp/src/thrift/parse/t_program.h b/compiler/cpp/src/thrift/parse/t_program.h
index 5b1b8d0..140dc35 100644
--- a/compiler/cpp/src/thrift/parse/t_program.h
+++ b/compiler/cpp/src/thrift/parse/t_program.h
@@ -291,14 +291,6 @@
         pwarning(1, "Namespace 'smalltalk' is deprecated. Use 'st' instead");
         base_language = "st";
       }
-      else if (base_language == "csharp") {
-        pwarning(1, "The '%s' target is no longer available. Use 'netstd' instead.", base_language.c_str());
-        // warn only, don't change base_language
-      }
-      else if (base_language == "netcore") {
-        pwarning(1, "The '%s' target is no longer available. Use 'netstd' instead.", base_language.c_str());
-        // warn only, don't change base_language
-      }
 
       t_generator_registry::gen_map_t my_copy = t_generator_registry::get_generator_map();