diff --git a/package/iptables/Makefile b/package/iptables/Makefile
index e637771871..2647f68397 100644
--- a/package/iptables/Makefile
+++ b/package/iptables/Makefile
@@ -27,7 +27,7 @@ include $(INCLUDE_DIR)/package.mk
 ifeq ($(DUMP),)
   -include $(LINUX_DIR)/.config
   include $(INCLUDE_DIR)/netfilter.mk
-  STAMP_CONFIGURED:=$(strip $(STAMP_CONFIGURED))_$(shell grep 'NETFILTER' $(LINUX_DIR)/.config | md5s)
+  STAMP_CONFIGURED:=$(strip $(STAMP_CONFIGURED))_$(shell $(SH_FUNC) grep 'NETFILTER' $(LINUX_DIR)/.config | md5s)
 endif