diff --git a/awall/model.lua b/awall/model.lua
index 43da3881c81b639a98c7f886c229cb9b2c826b11..3665d7ff1d0899b5e83f3ae5670b1e6ad322eb22 100644
--- a/awall/model.lua
+++ b/awall/model.lua
@@ -150,9 +150,7 @@ function Rule:zoneoptfrags()
       for i = 1,math.max(1, table.maxn(self.out)) do
 	 ozone = self.out[i]
 	 if izone ~= ozone or not izone then
-	    for i, ofrags in ipairs(zonepair(izone, ozone)) do
-	       table.insert(res, ofrags)
-	    end
+	    util.extend(res, zonepair(izone, ozone))
 	 end
       end
    end
@@ -183,9 +181,7 @@ function Rule:servoptfrags()
 
 	    if new or ports[sdef.proto][1] then
 	       if sdef.port then
-		  for i, port in util.listpairs(sdef.port) do
-		     table.insert(ports[sdef.proto], port)
-		  end
+		  util.extend(ports[sdef.proto], sdef.port)
 	       else ports[sdef.proto] = {} end
 	    end
 
@@ -329,9 +325,7 @@ function Rule:trules()
       end      
    end
 
-   for i, ofrag in ipairs(ffilter(self:extraoptfrags())) do
-      table.insert(res, ofrag)
-   end
+   util.extend(res, ffilter(self:extraoptfrags()))
 
    tag(res, 'table', self:table(), false)
    
diff --git a/awall/util.lua b/awall/util.lua
index 19a003d70ede38f2b3ec80d51c68fca785f02bab..f5afb374c57b02502ff8ee7ab4ef3c63e00882bc 100644
--- a/awall/util.lua
+++ b/awall/util.lua
@@ -9,7 +9,9 @@ module(..., package.seeall)
 
 local function list(var)
    if not var then return {} end
-   return type(var) == 'table' and var[1] and var or {var}
+   if type(var) ~= 'table' then return {var} end
+   if not next(var) then return {} end
+   return var[1] and var or {var}
 end
 
 function listpairs(var)
@@ -31,3 +33,7 @@ function contains(tbl, value)
    for k, v in pairs(tbl) do if v == value then return true end end
    return false
 end
+
+function extend(tbl1, tbl2)
+   for i, var in listpairs(tbl2) do table.insert(tbl1, var) end
+end