diff --git a/src/link/lexer.l b/src/link/lexer.l
index afbfb4a3..1461b618 100644
--- a/src/link/lexer.l
+++ b/src/link/lexer.l
@@ -28,6 +28,8 @@
 
 #include "parser.h"
 
+extern int yyparse();
+
 /* File include stack. */
 
 #define	MAX_INCLUDE_DEPTH 8