diff --git a/core/src/main/java/jenkins/model/experimentalflags/RemoveYuiUserExperimentalFlag.java b/core/src/main/java/jenkins/model/experimentalflags/RemoveYuiUserExperimentalFlag.java
index e8f8dcc31775..418f9c4b5406 100644
--- a/core/src/main/java/jenkins/model/experimentalflags/RemoveYuiUserExperimentalFlag.java
+++ b/core/src/main/java/jenkins/model/experimentalflags/RemoveYuiUserExperimentalFlag.java
@@ -24,8 +24,10 @@
 
 package jenkins.model.experimentalflags;
 
+import edu.umd.cs.findbugs.annotations.NonNull;
 import edu.umd.cs.findbugs.annotations.Nullable;
 import hudson.Extension;
+import jenkins.util.SystemProperties;
 import org.kohsuke.accmod.Restricted;
 import org.kohsuke.accmod.restrictions.NoExternalUse;
 
@@ -46,4 +48,10 @@ public String getDisplayName() {
     public String getShortDescription() {
         return "Remove YUI from all Jenkins UI pages. This will break anything that depends on YUI";
     }
+
+    @NonNull
+    @Override
+    public Boolean getDefaultValue() {
+        return SystemProperties.getBoolean(RemoveYuiUserExperimentalFlag.class.getName() + ".defaultValue", true);
+    }
 }
diff --git a/war/src/main/webapp/scripts/hudson-behavior.js b/war/src/main/webapp/scripts/hudson-behavior.js
index 9ae3d9298d37..043dc4677375 100644
--- a/war/src/main/webapp/scripts/hudson-behavior.js
+++ b/war/src/main/webapp/scripts/hudson-behavior.js
@@ -194,16 +194,6 @@ var resURL = "not-defined-yet"; // eslint-disable-line no-unused-vars
   }
 })();
 
-(function initializeYUIDebugLogReader() {
-  Behaviour.addLoadEvent(function () {
-    var logReaderElement = document.getElementById("yui-logreader");
-    if (logReaderElement !== null) {
-      var logReader = new YAHOO.widget.LogReader("yui-logreader");
-      logReader.collapse();
-    }
-  });
-})();
-
 // Form check code
 //========================================================
 var FormChecker = {