diff --git a/core/src/main/java/hudson/ClassicPluginStrategy.java b/core/src/main/java/hudson/ClassicPluginStrategy.java
index 356e6e8e9065..13976387db19 100644
--- a/core/src/main/java/hudson/ClassicPluginStrategy.java
+++ b/core/src/main/java/hudson/ClassicPluginStrategy.java
@@ -717,5 +717,5 @@ protected URL findResource(String name) {
     }
 
     @SuppressFBWarnings(value = "MS_SHOULD_BE_FINAL", justification = "Accessible via System Groovy Scripts")
-    public static /* not final */ boolean useAntClassLoader = SystemProperties.getBoolean(ClassicPluginStrategy.class.getName() + ".useAntClassLoader", true);
+    public static /* not final */ boolean useAntClassLoader = SystemProperties.getBoolean(ClassicPluginStrategy.class.getName() + ".useAntClassLoader");
 }