--- a/testing/raptor/raptor/manifest.py
+++ b/testing/raptor/raptor/manifest.py
@@ -162,27 +162,33 @@ def write_test_settings_json(args, test_
             subtest_lower_is_better)
 
     if test_details.get("alert_threshold", None) is not None:
         test_settings['raptor-options']['alert_threshold'] = float(test_details['alert_threshold'])
 
     if test_details.get("screen_capture", None) is not None:
         test_settings['raptor-options']['screen_capture'] = test_details.get("screen_capture")
 
-    # if gecko profiling is enabled, write profiling settings for webext
+    # if Gecko profiling is enabled, write profiling settings for webext
     if test_details.get("gecko_profile", False):
-        test_settings['raptor-options']['gecko_profile'] = True
-        # when profiling, if webRender is enabled we need to set that, so
-        # the runner can add the web render threads to gecko profiling
-        test_settings['raptor-options']['gecko_profile_interval'] = \
-            float(test_details.get("gecko_profile_interval", 0))
-        test_settings['raptor-options']['gecko_profile_entries'] = \
-            float(test_details.get("gecko_profile_entries", 0))
-        if str(os.getenv('MOZ_WEBRENDER')) == '1':
-            test_settings['raptor-options']['webrender_enabled'] = True
+        threads = 'GeckoMain,Compositor'
+
+        # With WebRender enabled profile some extra threads
+        if os.getenv('MOZ_WEBRENDER') == '1':
+            threads = '{},Renderer,WR'.format(threads)
+
+        if test_details.get('gecko_profile_threads'):
+            threads = '{0},{1}'.format(threads, test_details.get('gecko_profile_threads'))
+
+        test_settings['raptor-options'].update({
+            'gecko_profile': True,
+            'gecko_profile_entries': int(test_details.get('gecko_profile_entries')),
+            'gecko_profile_interval': int(test_details.get('gecko_profile_interval')),
+            'gecko_profile_threads': threads,
+        })
 
     if test_details.get("newtab_per_cycle", None) is not None:
         test_settings['raptor-options']['newtab_per_cycle'] = \
             bool(test_details['newtab_per_cycle'])
 
     settings_file = os.path.join(tests_dir, test_details['name'] + '.json')
     try:
         with open(settings_file, 'w') as out_file:

--- a/testing/raptor/webext/raptor/runner.js
+++ b/testing/raptor/webext/raptor/runner.js
@@ -56,17 +56,17 @@ var isFCPPending = false;
 var isDCFPending = false;
 var isTTFIPending = false;
 var isLoadTimePending = false;
 var isBenchmarkPending = false;
 var pageTimeout = 10000; // default pageload timeout
 var geckoProfiling = false;
 var geckoInterval = 1;
 var geckoEntries = 1000000;
-var webRenderEnabled = false;
+var geckoThreads = [];
 var debugMode = 0;
 var screenCapture = false;
 
 var results = {"name": "",
                "page": "",
                "type": "",
                "browser_cycle": 0,
                "expected_browser_cycles": 0,
@@ -111,30 +111,23 @@ function getTestSettings() {
         results.expected_browser_cycles = settings.expected_browser_cycles;
         results.cold = settings.cold;
         results.unit = settings.unit;
         results.subtest_unit = settings.subtest_unit;
         results.lower_is_better = settings.lower_is_better === true;
         results.subtest_lower_is_better = settings.subtest_lower_is_better === true;
         results.alert_threshold = settings.alert_threshold;
 
-        if (settings.gecko_profile !== undefined) {
-          if (settings.gecko_profile === true) {
-            geckoProfiling = true;
-            results.extra_options = ["gecko_profile"];
-            if (settings.gecko_profile_interval !== undefined) {
-              geckoInterval = settings.gecko_profile_interval;
-            }
-            if (settings.gecko_profile_entries !== undefined) {
-              geckoEntries = settings.gecko_profile_entries;
-            }
-            if (settings.webrender_enabled !== undefined) {
-              webRenderEnabled = settings.webrender_enabled;
-            }
-          }
+        if (settings.gecko_profile === true) {
+          results.extra_options = ["gecko_profile"];
+
+          geckoProfiling = true;
+          geckoEntries = settings.gecko_profile_entries;
+          geckoInterval = settings.gecko_profile_interval;
+          geckoThreads = settings.gecko_profile_threads;
         }
 
         if (settings.screen_capture !== undefined) {
           screenCapture = settings.screen_capture;
         }
 
         if (settings.newtab_per_cycle !== undefined) {
           reuseTab = settings.newtab_per_cycle;
@@ -313,30 +306,23 @@ function onCaptured(screenshotUri) {
   postToControlServer("screenshot", [screenshotUri, testName, pageCycle]);
 }
 
 function onError(error) {
   console.log("Screenshot captured failed!");
   console.log(`Error: ${error}`);
 }
 
-
 async function startGeckoProfiling() {
-  var _threads;
-  if (webRenderEnabled) {
-    _threads = ["GeckoMain", "Compositor", "WR", "Renderer"];
-  } else {
-    _threads = ["GeckoMain", "Compositor"];
-  }
-  postToControlServer("status", "starting gecko profiling");
+  postToControlServer("status", `starting Gecko profiling for threads: ${geckoThreads}`);
   await browser.geckoProfiler.start({
     bufferSize: geckoEntries,
     interval: geckoInterval,
     features: ["js", "leaf", "stackwalk", "threads", "responsiveness"],
-    threads: _threads,
+    threads: geckoThreads.split(","),
   });
 }
 
 async function stopGeckoProfiling() {
   postToControlServer("status", "stopping gecko profiling");
   await browser.geckoProfiler.stop();
 }