diff --git a/src/flow-filter.c b/src/flow-filter.c
index cb51aa2..3c1bfea 100644
--- a/src/flow-filter.c
+++ b/src/flow-filter.c
@@ -56,7 +56,7 @@
 int debug;
 int ip_net_only;
 
-struct acl_list acl_list;
+extern struct acl_list acl_list;
 
 int yyparse (void);
 void usage(void);