diff --git a/vars/tasks.groovy b/vars/tasks.groovy
index 9de4c78322d3e..3ff9a7b4850ae 100644
--- a/vars/tasks.groovy
+++ b/vars/tasks.groovy
@@ -42,7 +42,13 @@ def test() {
 }
 
 def functionalOss(Map params = [:]) {
-  def config = params ?: [ciGroups: true, firefox: true, accessibility: true, pluginFunctional: true, visualRegression: false]
+  def config = params ?: [
+    ciGroups: true,
+    firefox: !githubPr.isPr(),
+    accessibility: true,
+    pluginFunctional: true,
+    visualRegression: false
+  ]
 
   task {
     kibanaPipeline.buildOss(6)
@@ -73,7 +79,7 @@ def functionalOss(Map params = [:]) {
 def functionalXpack(Map params = [:]) {
   def config = params ?: [
     ciGroups: true,
-    firefox: true,
+    firefox: !githubPr.isPr(),
     accessibility: true,
     pluginFunctional: true,
     savedObjectsFieldMetrics: true,