diff --git a/sipgen/parser.y b/sipgen/parser.y
index 2ed1b4e..05a12c1 100644
--- a/sipgen/parser.y
+++ b/sipgen/parser.y
@@ -24,6 +24,7 @@
 #include "sip.h"
 
 void yyerror(char* s);
+int yylex();
 
 #define MAX_NESTED_IF       10
 #define MAX_NESTED_SCOPE    10