diff --git a/lib/iptables.inc b/lib/iptables.inc
index 38e8c9c..76d938b 100644
--- a/lib/iptables.inc
+++ b/lib/iptables.inc
@@ -184,8 +184,8 @@ function enable_mss_clamp {
 			[[ -z ${msssize} ]] && msssize="-"
 			[[ ${msssize} != "-" ]] && msssize="--set-mss ${msssize}"
 			[[ ${msssize} == "-" ]] && msssize="--clamp-mss-to-pmtu"
-			[[ ${interface} == "all" ]] && interface=""
 			[[ ${interface} != "all" ]] && interface="-o ${interface}"
+			[[ ${interface} == "all" ]] && interface=""
 			${debug} ${DebugColor} "${FUNCNAME}:${DEFAULT_COLOR} Read: ${interface} ${mss} ${type} ${msssize}"
 			${VER_IPTABLES} -A ${type} -p tcp --tcp-flags SYN,RST SYN -j TCPMSS \
 				 ${interface} -m tcpmss --mss ${mss} ${msssize}