diff --git a/sim/gate.lua b/sim/gate.lua
index 7e64d3b..1066b19 100644
--- a/sim/gate.lua
+++ b/sim/gate.lua
@@ -28,8 +28,8 @@ function Gate.addport(self, port)
 	Port.setgate(port, self)
 end
 
-function Gate.getportstate(self, index)
-	return self.ports[index].group.state
+function Gate.getportstate(gate, index)
+	return gate.ports[index].group.state
 end
 
 function Gate.setportstate(self, index, state)
diff --git a/sim/group.lua b/sim/group.lua
index 4fffb05..f6c2ed0 100644
--- a/sim/group.lua
+++ b/sim/group.lua
@@ -118,7 +118,7 @@ function Group.addport(self, port)
 		self.in_ports[port] = port
 		self.nin_ports = self.nin_ports + 1
 		if port.causeupdate then
-			self.in_ports_update[port] = port
+			table.insert(self.in_ports_update, port)
 		end
 		
 		Simulation.queuegate(GSim, Port.getgate(port))
@@ -147,7 +147,7 @@ function Group.removeport(self, port)
 		self.in_ports[port] = nil
 		self.nin_ports = self.nin_ports - 1
 		if port.causeupdate then
-			self.in_ports_update[port] = nil
+			array_remove(self.in_ports_update, port)
 		end
 		
 		Simulation.queuegate(GSim, Port.getgate(port))
@@ -198,7 +198,7 @@ function Group.setstate(self, state)
 		self.state = state
 		self.updatetick = sim.currenttick
 		
-		for k, port in pairs(self.in_ports_update) do
+		for k, port in ipairs(self.in_ports_update) do
 			Simulation.queuegate(sim, Port.getgate(port))
 		end
 		
diff --git a/sim/main.lua b/sim/main.lua
index abc1268..cac837f 100644
--- a/sim/main.lua
+++ b/sim/main.lua
@@ -262,7 +262,7 @@ while 1 do
 					local group = Wire.getgroup(wire)
 					local numwires  = 0; for k, wire2 in pairs(group.wires          ) do numwires  = numwires +1 end
 					local numportsi = 0; for k, port  in pairs(group.in_ports       ) do numportsi = numportsi+1 end
-					local numportsu = 0; for k, port  in pairs(group.in_ports_update) do numportsu = numportsu+1 end
+					local numportsu = #group.in_ports_update
 					local numportso = 0; local numportson=0;
 					for k, port  in pairs(group.out_ports) do
 						numportso = numportso+1
diff --git a/sim/simulation.lua b/sim/simulation.lua
index 44cd992..220c0bd 100644
--- a/sim/simulation.lua
+++ b/sim/simulation.lua
@@ -270,18 +270,6 @@ function Simulation.queuegroup(self, group)
 	end
 end
 
-local function array_remove(array, value)
-	for i = 1, #array do
-		local v = array[i]
-		if v==value then
-			array[i] = array[#array]
-			array[#array] = nil
-			return
-		end
-	end
-	error("element not in array")
-end
-
 function Simulation.dequeuegroup(self, group)
 	if group.in_queue then
 		array_remove(self.groupqueue, group)
diff --git a/sim/utility.lua b/sim/utility.lua
index a5f5034..8c0684e 100644
--- a/sim/utility.lua
+++ b/sim/utility.lua
@@ -66,3 +66,14 @@ function tobitstring(num, len)
 	return bitstring
 end
 
+function array_remove(array, value)
+	for i = 1, #array do
+		local v = array[i]
+		if v==value then
+			array[i] = array[#array]
+			array[#array] = nil
+			return
+		end
+	end
+	error("element not in array")
+end