diff --git a/sipgen/lexer.l b/sipgen/lexer.l
index 91032cc..a310e66 100644
--- a/sipgen/lexer.l
+++ b/sipgen/lexer.l
@@ -21,6 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#include <unistd.h>
 
 #include "sip.h"
 #include "parser.h"
diff --git a/sipgen/parser.y b/sipgen/parser.y
index 7670cab..3191362 100644
--- a/sipgen/parser.y
+++ b/sipgen/parser.y
@@ -23,6 +23,7 @@
 
 #include "sip.h"
 
+int yyerror(const char* s);
 
 #define MAX_NESTED_IF       10
 #define MAX_NESTED_SCOPE    10