diff --git a/addon/content/modules/pEpServer.js b/addon/content/modules/pEpServer.js
index 28ca3bc..130c73f 100644
--- a/addon/content/modules/pEpServer.js
+++ b/addon/content/modules/pEpServer.js
@@ -75,6 +75,8 @@ class pEpServer {
       // are handled below.
       return response;
     }).catch((err) => {
+      // On Linux this is triggered with the "close session" call. Just ignore.
+      if (functionName == "close_session") return Promise.resolve(null);
       this.log.info("XMLHttpRequest failed first time. Maybe sleep/wake cycle. Retrying ...");
       // This file is used in the test suite, hence calling this at the top doesn't work.
       let { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
diff --git a/addon/experiments.js b/addon/experiments.js
index 95e004d..d1226b1 100644
--- a/addon/experiments.js
+++ b/addon/experiments.js
@@ -134,13 +134,27 @@ var pEp4Tb = class extends ExtensionCommon.ExtensionAPI {
 
     ExtensionSupport.unregisterWindowListener(EXTENSION_NAME);
 
+    let { pEpController } = ChromeUtils.import("chrome://pEp4Tb/content/pEpController.js");
+
     for (let win of Services.wm.getEnumerator("mail:3pane")) {
-      unpaint(win);
+      if (isAppShutdown) {
+        // Make sure the controller gets shut down.
+        pEpController.shutdown();
+      } else {
+        unpaint(win);
+      }
     }
     for (let win of Services.wm.getEnumerator("msgcompose")) {
-      unpaint(win);
+      if (isAppShutdown) {
+        // Make sure the controller gets shut down.
+        pEpController.shutdown();
+      } else {
+        unpaint(win);
+      }
     }
 
+    if (isAppShutdown) return;
+
     // Unload all modules.
     Cu.unload("chrome://pEp4Tb/content/modules/handshake.js");
     Cu.unload("chrome://pEp4Tb/content/modules/pEp.js");
@@ -166,8 +180,6 @@ var pEp4Tb = class extends ExtensionCommon.ExtensionAPI {
     Cu.unload("chrome://pEp4Tb/content/TbSync.js");
     Cu.unload("chrome://pEp4Tb/content/modules/sync.js");
 
-    if (isAppShutdown) return;
-
     this.chromeHandle.destruct();
     this.chromeHandle = null;
     // Looks like we got uninstalled. Maybe a new version will be installed now.