diff --git a/extensions/ipset/Makefile.am b/extensions/ipset/Makefile.am
index 2603ca6..b9a7d65 100644
--- a/extensions/ipset/Makefile.am
+++ b/extensions/ipset/Makefile.am
@@ -1,6 +1,7 @@
 # -*- Makefile -*-
 
-AM_CFLAGS = ${regular_CFLAGS} -DIPSET_LIB_DIR=\"${xtlibdir}\"
+AM_CFLAGS = ${regular_CFLAGS} -DIPSET_LIB_DIR=\"${xtlibdir}\" \
+            -DIP_NF_SET_HASHSIZE=1024
 
 include ../../Makefile.extra