diff --git a/src/tools/vppapigen/lex.h b/src/tools/vppapigen/lex.h
new file mode 100644
index 0000000..a0fdc73
--- /dev/null
+++ b/src/tools/vppapigen/lex.h
@@ -0,0 +1,50 @@
+/*
+ *------------------------------------------------------------------
+ * lex.h - definitions for the api generator's lexical
+ * analyzer.
+ *
+ * Copyright (c) 1996-2009 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *------------------------------------------------------------------
+ */
+
+#ifndef _LEX_H_
+#define _LEX_H_ 1
+
+extern int yylex (void);
+extern void yyerror (char *);
+extern int yyparse (void);
+
+#ifndef YYSTYPE
+#define YYSTYPE void *
+#endif
+
+#include "tools/vppapigen/gram.h"
+
+enum lex_state {
+    START_STATE = 1,
+    NAME_STATE,
+    NUMBER_STATE,
+    C_COMMENT_STATE,
+    CPP_COMMENT_STATE,
+    STRING_STATE,
+    HELPER_STATE,
+    LINE_PRAGMA_STATE,
+};
+
+#define MAXNAME 64000
+
+extern unsigned long input_crc;
+extern unsigned long message_crc;
+
+#endif /* _LEX_H_ */