diff --git a/chrome/content/zotero/xpcom/server/saveSession.js b/chrome/content/zotero/xpcom/server/saveSession.js
index e40bad3931..de1558affe 100644
--- a/chrome/content/zotero/xpcom/server/saveSession.js
+++ b/chrome/content/zotero/xpcom/server/saveSession.js
@@ -49,9 +49,9 @@ Zotero.Server.Connector.SessionManager = {
 		var ttl = this._sessions.size >= 10 ? 60 : 600;
 		var deleteBefore = new Date() - ttl * 1000;
 
-		for (let session of this._sessions) {
+		for (let [id, session] of this._sessions) {
 			if (session.created < deleteBefore) {
-				this._session.delete(session.id);
+				this._sessions.delete(id);
 			}
 		}
 	}
@@ -147,7 +147,7 @@ Zotero.Server.Connector.SaveSession = class {
 	}
 
 	remove() {
-		delete Zotero.Server.Connector.SessionManager._sessions[this.id];
+		Zotero.Server.Connector.SessionManager._sessions.delete(this.id);
 	}
 
 	/**
diff --git a/chrome/content/zotero/xpcom/server/server.js b/chrome/content/zotero/xpcom/server/server.js
index 23bfa30448..588971096a 100755
--- a/chrome/content/zotero/xpcom/server/server.js
+++ b/chrome/content/zotero/xpcom/server/server.js
@@ -513,7 +513,7 @@ Zotero.Server.RequestHandler.prototype._processEndpoint = async function (method
 		}
 	} catch(e) {
 		Zotero.debug(e);
-		this._requestFinished(this._generateResponse(500), "text/plain", "An error occurred\n");
+		this._requestFinished(this._generateResponse(500, "text/plain", "An error occurred\n"));
 		throw e;
 	}
 };
diff --git a/test/tests/server_connectorTest.js b/test/tests/server_connectorTest.js
index ca19f95b97..a30fb9f10c 100644
--- a/test/tests/server_connectorTest.js
+++ b/test/tests/server_connectorTest.js
@@ -93,6 +93,41 @@ describe("Connector Server", function () {
 		});
 	});
 
+	describe("SaveSession.SessionManager", function () {
+		var SessionManager = Zotero.Server.Connector.SessionManager;
+
+		it("should expire sessions older than the TTL when gc() runs", function () {
+			var id = "gcOld_" + Zotero.Utilities.randomString();
+			var session = SessionManager.create(id, 'saveItems', {});
+			// Backdate creation beyond the 10-minute TTL
+			session.created = new Date(Date.now() - 11 * 60 * 1000);
+
+			SessionManager.gc();
+
+			assert.isUndefined(SessionManager.get(id), "stale session should be removed by gc()");
+		});
+
+		it("should keep sessions newer than the TTL when gc() runs", function () {
+			var id = "gcNew_" + Zotero.Utilities.randomString();
+			var session = SessionManager.create(id, 'saveItems', {});
+
+			SessionManager.gc();
+
+			assert.strictEqual(SessionManager.get(id), session, "fresh session should survive gc()");
+			session.remove();
+		});
+
+		it("should remove a session via SaveSession#remove()", function () {
+			var id = "remove_" + Zotero.Utilities.randomString();
+			var session = SessionManager.create(id, 'saveItems', {});
+			assert.strictEqual(SessionManager.get(id), session);
+
+			session.remove();
+
+			assert.isUndefined(SessionManager.get(id), "remove() should delete the session from the manager");
+		});
+	});
+
 	describe('/connector/getTranslatorCode', function () {
 		it('should respond with translator code', async function () {
 			var code = 'function detectWeb() {}\nfunction doImport() {}';