diff -Nurd gnuchess-5.08.orig/src/pgn.c gnuchess-5.08/src/pgn.c
--- gnuchess-5.08.orig/src/pgn.c	2010-01-03 06:18:13.000000000 -0500
+++ gnuchess-5.08/src/pgn.c	2021-06-12 23:43:30.000000000 -0400
@@ -40,6 +40,8 @@
 
 extern FILE *yyin;
 
+extern int yylex (void);
+
 void PGNSaveToFile (const char *file, const char *resultstr)
 /****************************************************************************
  *