diff --git a/acconfig.h b/acconfig.h
index ae08a75de..fb2903349 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -66,6 +66,8 @@
 #undef NO_SYS_ERRLIST
 #undef NO_SYS_SIGLIST
 
+#undef WITH_SYMBOL_UNDERSCORE
+
 #undef SIZEOF_CHAR
 #undef SIZEOF_SHORT
 #undef SIZEOF_LONG