diff --git a/packages/slave/slave.js b/packages/slave/slave.js
index 47cfb3bb..b717228e 100755
--- a/packages/slave/slave.js
+++ b/packages/slave/slave.js
@@ -1059,8 +1059,8 @@ class Slave extends libLink.Link {
 		let updateList = (list, updatedList, prop, event) => {
 			let added = new Set(updatedList);
 			let removed = new Set(list);
-			list.forEach(Set.prototype.delete.bind(added));
-			updatedList.forEach(Set.prototype.delete.bind(removed));
+			list.forEach(el => added.delete(el));
+			updatedList.forEach(el => removed.delete(el));
 
 			for (let name of added) {
 				list.add(name);
@@ -1080,15 +1080,14 @@ class Slave extends libLink.Link {
 		updateList(this.adminlist, message.data.adminlist, "admin", libLink.messages.adminlistUpdate);
 		updateList(this.whitelist, message.data.whitelist, "whitelisted", libLink.messages.whitelistUpdate);
 
-		let updatedBanlist = new Map(message.data.banlist);
-		let addedOrChanged = new Map(updatedBanlist);
+		let addedOrChanged = new Map(message.data.banlist);
 		let removed = new Set(this.banlist.keys());
-		removed.forEach((name, reason) => {
+		addedOrChanged.forEach((_, name) => removed.delete(name));
+		this.banlist.forEach((reason, name) => {
 			if (addedOrChanged.get(name) === reason) {
 				addedOrChanged.delete(name);
 			}
 		});
-		updatedBanlist.forEach(Set.prototype.delete.bind(removed));
 
 		for (let [name, reason] of addedOrChanged) {
 			this.banlist.set(name, reason);
diff --git a/plugins/statistics_exporter/instance.js b/plugins/statistics_exporter/instance.js
index 002e51f6..001d96b6 100644
--- a/plugins/statistics_exporter/instance.js
+++ b/plugins/statistics_exporter/instance.js
@@ -21,6 +21,17 @@ const instanceGameFlowStatistics = new Gauge(
 	{ labels: ["instance_id", "statistic", "direction", "name"] },
 );
 
+function setForceFlowStatistic(instanceId, forceName, statisticName, direction, item, value) {
+	instanceForceFlowStatistics.labels(String(instanceId), forceName, statisticName, direction, item).set(value);
+
+	// For item and fluid statistics it's useful to compare the input flow with the
+	// output flow, to simplify the comparison ensure both directions have a value.
+	if (["item_production_statistics", "fluid_production_statistic"].includes(statisticName)) {
+		let reverseDirection = direction === "input" ? "output" : "input";
+		instanceForceFlowStatistics.labels(String(instanceId), forceName, statisticName, reverseDirection, item);
+	}
+}
+
 
 class InstancePlugin extends libPlugin.BaseInstancePlugin {
 	async init() {
@@ -46,9 +57,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 			for (let [statisticName, statistic] of Object.entries(flowStatistics)) {
 				for (let [direction, counts] of Object.entries(statistic)) {
 					for (let [item, value] of Object.entries(counts)) {
-						instanceForceFlowStatistics.labels(
-							String(instanceId), forceName, statisticName, direction, item
-						).set(value);
+						setForceFlowStatistic(instanceId, forceName, statisticName, direction, item, value);
 					}
 				}
 			}
diff --git a/test/slave.js b/test/slave.js
index 7e0801e1..f436b312 100644
--- a/test/slave.js
+++ b/test/slave.js
@@ -162,4 +162,85 @@ describe("Slave testing", function() {
 			]));
 		});
 	});
+
+	describe("class Slave", function() {
+		describe(".syncUserListsEventHandler()", function() {
+			let mockSlave;
+			beforeEach(function() {
+				mockSlave = {
+					adminlist: new Set(),
+					whitelist: new Set(),
+					banlist: new Map(),
+					broadcasts: [],
+					broadcastEventToInstance(message, event) {
+						this.broadcasts.push(message["data"]);
+					},
+					syncUserListsEventHandler: slave._Slave.prototype.syncUserListsEventHandler,
+					syncLists(adminlist, banlist, whitelist) {
+						return this.syncUserListsEventHandler({ "data": {
+							"adminlist": adminlist,
+							"banlist": banlist,
+							"whitelist": whitelist,
+						}});
+					},
+				};
+			});
+
+			it("should broadcast new entries to adminlist", async function() {
+				await mockSlave.syncLists(["admin1"], [], []);
+				await mockSlave.syncLists(["admin1", "admin2"], [], []);
+
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "admin1", "admin": true },
+					{ "name": "admin2", "admin": true },
+				]);
+			});
+
+			it("should broadcast removals from adminlist", async function() {
+				mockSlave.adminlist.add("admin1").add("admin2");
+				await mockSlave.syncLists(["admin1"], [], []);
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "admin2", "admin": false },
+				]);
+			});
+
+			it("should broadcast new entries to whitelist", async function() {
+				await mockSlave.syncLists([], [], ["player1"]);
+				await mockSlave.syncLists([], [], ["player1", "player2"]);
+
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "player1", "whitelisted": true },
+					{ "name": "player2", "whitelisted": true },
+				]);
+			});
+
+			it("should broadcast removals from whitelist", async function() {
+				mockSlave.whitelist.add("player1").add("player2");
+				await mockSlave.syncLists([], [], ["player1"]);
+
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "player2", "whitelisted": false },
+				]);
+			});
+
+			it("should broadcast new entries to banlist", async function() {
+				await mockSlave.syncLists([], [["badie1", "greifing"]], []);
+				await mockSlave.syncLists([], [["badie1", "greifing"], ["badie2", "annoying"]], []);
+
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "badie1", "banned": true, "reason": "greifing" },
+					{ "name": "badie2", "banned": true, "reason": "annoying" },
+				]);
+			});
+
+			it("should broadcast removals to banlist", async function() {
+				mockSlave.banlist.set("badie1", "greifing").set("badie2", "annoying");
+				await mockSlave.syncLists([], [["badie1", "greifing"]], []);
+
+				assert.deepEqual(mockSlave.broadcasts, [
+					{ "name": "badie2", "banned": false, "reason": "" },
+				]);
+			});
+		});
+	});
 });