diff --git a/flash.h b/flash.h
index 282a44d..3d86836 100644
--- a/flash.h
+++ b/flash.h
@@ -480,6 +480,7 @@
 #define printf_debug(x...) { if (verbose) printf(x); }
 
 /* flashrom.c */
+void mmap_errmsg();
 int map_flash_registers(struct flashchip *flash);
 
 /* layout.c */