diff --git a/lm-c99/ig-c99.ysl2 b/lm-c99/ig-c99.ysl2
index 2e5d1fd..47c3191 100644
--- a/lm-c99/ig-c99.ysl2
+++ b/lm-c99/ig-c99.ysl2
@@ -119,15 +119,21 @@ tstylesheet {
     }
 
 
-
-
     // ----------------------------------------------------------------------
     // pEpACIDLang IG-C99
     // The C99 Interface Generator for pEpACIDLang
     // ----------------------------------------------------------------------
 
-    // generate basetype declarations defined by the idl
+    // The idl-api owns the root template and executes validation
+    // of the interface description.
+    // Errors will be printed to stdout.
+    // After successful validation, the idl-api applies the
+    // template called "pEpACIDLang"
+    template "pEpACIDLang" {
+        apply "idl|package", 0
+    }
 
+    // generate basetype declarations defined by the idl
     template "idl" document "ig-c99/idl_core.h", "text" {
         ||
         #pragma once
@@ -156,6 +162,9 @@ tstylesheet {
         }
     }
 
+    template "package" {
+        apply "api", 0
+    }
 
     template "api" document "ig-c99/{@name}_api.h", "text" {
         const "api_name", "@name";