diff --git a/packages/lib/link/connectors.js b/packages/lib/link/connectors.js
index ef78fefd..91a6f995 100644
--- a/packages/lib/link/connectors.js
+++ b/packages/lib/link/connectors.js
@@ -75,6 +75,9 @@ class WebSocketBaseConnector extends events.EventEmitter {
 	 * Start sending heartbeats
 	 */
 	startHeartbeat() {
+		if (this._heartbeatId) {
+			throw new Error("heartbeat is already running");
+		}
 		this._lastHeartbeat = Date.now();
 		this._heartbeatId = setInterval(() => {
 			this._doHeartbeat();
diff --git a/packages/master/master.js b/packages/master/master.js
index aec2aa05..54ac0933 100755
--- a/packages/master/master.js
+++ b/packages/master/master.js
@@ -1399,7 +1399,24 @@ class WebSocketServerConnector extends libLink.WebSocketBaseConnector {
 	 * @param {number} lastSeq - The last message the client received.
 	 */
 	continue(socket, lastSeq) {
-		this._socket.terminate();
+
+		// It's possible the previous connection hasn't closed yet due to a
+		// stale connection.  If this is the case the connector will have to
+		// wait for the previous socket to close down before it can continue
+		// from a new socket, or there will be overlapping events from both.
+		if (["connected", "closing"].includes(this._state)) {
+			this._socket.close(4003, "Session Hijacked");
+
+			// Correctly waiting for the connector to close and then
+			// handling all the edge cases like multiple continues happening
+			// in parallel or connections going stale is far too difficult.
+			// Kill the connection here and let the client reconnect later
+			// when the connector is not held up by an active connection.
+			socket.close(1013, "Session Busy");
+			socket.terminate();
+			return;
+		}
+
 		this._socket = socket;
 
 		if (this._timeoutId) {
diff --git a/test/integration/clusterio.js b/test/integration/clusterio.js
index 47050662..389bd86c 100644
--- a/test/integration/clusterio.js
+++ b/test/integration/clusterio.js
@@ -2,11 +2,15 @@
 const assert = require("assert").strict;
 const fs = require("fs-extra");
 const path = require("path");
+const events = require("events");
 
 const libLink = require("@clusterio/lib/link");
 const libUsers = require("@clusterio/lib/users");
 
-const { slowTest, get, exec, execCtl, sendRcon, getControl, instancesDir } = require("./index");
+const {
+	TestControl, TestControlConnector, url, controlToken, slowTest,
+	get, exec, execCtl, sendRcon, getControl, instancesDir,
+} = require("./index");
 
 
 async function getInstances() {
@@ -32,6 +36,29 @@ describe("Integration of Clusterio", function() {
 				);
 			});
 		});
+
+		describe("run", function() {
+			it("should handle resume of an active connection", async function() {
+				slowTest(this);
+				let tlsCa = await fs.readFile("test/file/tls/cert.pem");
+				let connectorA = new TestControlConnector(url, 2, tlsCa);
+				connectorA.token = controlToken;
+				let controlA = new TestControl(connectorA);
+				await connectorA.connect();
+				connectorA._state = "closing";
+				connectorA.stopHeartbeat();
+				connectorA.on("error", () => {});
+
+				let connectorB = new TestControlConnector(url, 2, tlsCa);
+				connectorB.token = controlToken;
+				let controlB = new TestControl(connectorB);
+				connectorB._sessionToken = connectorA._sessionToken;
+				connectorB._state = "handshake";
+				await connectorB._doConnect();
+				await events.once(connectorB, "resume");
+				await connectorB.close();
+			});
+		});
 	});
 
 	describe("clusterioctl", function() {
diff --git a/test/integration/index.js b/test/integration/index.js
index be6eb761..d1588ae9 100644
--- a/test/integration/index.js
+++ b/test/integration/index.js
@@ -197,6 +197,7 @@ module.exports = {
 	getControl,
 
 	url,
+	controlToken,
 	instancesDir,
 	databaseDir,
 	masterConfigPath,