--- a/devtools/client/netmonitor/src/components/websockets/Toolbar.js
+++ b/devtools/client/netmonitor/src/components/websockets/Toolbar.js
@@ -47,16 +47,21 @@ class Toolbar extends Component {
       searchboxRef: PropTypes.object.isRequired,
       toggleFrameFilterType: PropTypes.func.isRequired,
       clearFrames: PropTypes.func.isRequired,
       setFrameFilterText: PropTypes.func.isRequired,
       frameFilterType: PropTypes.string.isRequired,
     };
   }
 
+  componentWillUnmount() {
+    const { setFrameFilterText } = this.props;
+    setFrameFilterText("");
+  }
+
   /**
    * Render a separator.
    */
   renderSeparator() {
     return span({ className: "devtools-separator" });
   }
 
   /**

--- a/devtools/client/netmonitor/test/browser.ini
+++ b/devtools/client/netmonitor/test/browser.ini
@@ -232,8 +232,9 @@ skip-if = (os == 'win' && os_version == 
 [browser_net_truncate.js]
 [browser_net_view-source-debugger.js]
 [browser_net_waterfall-click.js]
 [browser_net_websocket_stacks.js]
 [browser_net_worker_stacks.js]
 [browser_net_ws-basic.js]
 [browser_net_ws-clear.js]
 [browser_net_ws-filter-dropdown.js]
+[browser_net-ws-filter-freetext.js]

new file mode 100644
--- /dev/null
+++ b/devtools/client/netmonitor/test/browser_net-ws-filter-freetext.js
@@ -0,0 +1,90 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Test that WS connection is established successfully and filtering messages using freetext works correctly.
+ */
+
+add_task(async function() {
+  const { tab, monitor } = await initNetMonitor(WS_PAGE_URL);
+  info("Starting test... ");
+
+  const { document, store, windowRequire } = monitor.panelWin;
+  const Actions = windowRequire("devtools/client/netmonitor/src/actions/index");
+  const { getDisplayedFrames } = windowRequire(
+    "devtools/client/netmonitor/src/selectors/web-sockets"
+  );
+
+  store.dispatch(Actions.batchEnable(false));
+
+  // Wait for WS connection(s) to be established + send messages
+  await ContentTask.spawn(tab.linkedBrowser, {}, async () => {
+    await content.wrappedJSObject.openConnection(3);
+    await content.wrappedJSObject.openConnection(1);
+  });
+
+  const requests = document.querySelectorAll(".request-list-item");
+  is(requests.length, 2, "There should be two requests");
+
+  // Wait for all sent/received messages to be displayed in DevTools
+  wait = waitForDOM(
+    document,
+    "#messages-panel .ws-frames-list-table .ws-frame-list-item",
+    6
+  );
+
+  // Select the first request
+  EventUtils.sendMouseEvent({ type: "mousedown" }, requests[0]);
+
+  // Click on the "Messages" panel
+  EventUtils.sendMouseEvent(
+    { type: "click" },
+    document.querySelector("#messages-tab")
+  );
+  await wait;
+
+  // Get all messages present in the "Messages" panel
+  const frames = document.querySelectorAll(
+    "#messages-panel .ws-frames-list-table .ws-frame-list-item"
+  );
+
+  // Check expected results
+  is(frames.length, 6, "There should be six frames");
+
+  // Fill filter input with text and check displayed messages
+  const type = string => {
+    for (const ch of string) {
+      EventUtils.synthesizeKey(ch, {}, monitor.panelWin);
+    }
+  };
+  const filterInput = document.querySelector(
+    "#messages-panel .devtools-filterinput"
+  );
+  filterInput.focus();
+  type("Payload 2");
+
+  // Wait till the text filter is applied.
+  await waitUntil(() => getDisplayedFrames(store.getState()).length == 2);
+
+  const filteredFrames = document.querySelectorAll(
+    "#messages-panel .ws-frames-list-table .ws-frame-list-item"
+  );
+  is(filteredFrames.length, 2, "There should be two frames");
+
+  // Select the second request and check that the filter input is cleared
+  EventUtils.sendMouseEvent({ type: "mousedown" }, requests[1]);
+  const secondRequestFrames = document.querySelectorAll(
+    "#messages-panel .ws-frames-list-table .ws-frame-list-item"
+  );
+  is(secondRequestFrames.length, 2, "There should be two frames");
+  is(filterInput.value, "", "The filter input is cleared");
+
+  // Close WS connection
+  await ContentTask.spawn(tab.linkedBrowser, {}, async () => {
+    await content.wrappedJSObject.closeConnection();
+  });
+
+  await teardown(monitor);
+});