diff --git a/worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/util/ClassSourceValidator.java b/worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/util/ClassSourceValidator.java
index a9454c47..e0d32255 100644
--- a/worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/util/ClassSourceValidator.java
+++ b/worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/util/ClassSourceValidator.java
@@ -47,14 +47,17 @@ public class ClassSourceValidator {
 
     private static final String SEPARATOR_LINE = Strings.repeat("*", 46);
     private static final Method loadClass;
+    private static Class<?> pluginClassLoaderClass;
 
     static {
         Method tmp;
         try {
-            tmp = PluginClassLoader.class.getDeclaredMethod("loadClass0",
+            pluginClassLoaderClass = Class.forName("org.bukkit.plugin.java.PluginClassLoader", false,
+                    Bukkit.class.getClassLoader());
+            tmp = pluginClassLoaderClass.getDeclaredMethod("loadClass0",
                     String.class, boolean.class, boolean.class, boolean.class);
             tmp.setAccessible(true);
-        } catch (NoSuchMethodException e) {
+        } catch (NoSuchMethodException | ClassNotFoundException e) {
             tmp = null;
         }
         loadClass = tmp;
@@ -95,7 +98,7 @@ public class ClassSourceValidator {
                 continue;
             }
             ClassLoader targetLoader = target.getClass().getClassLoader();
-            if (!(targetLoader instanceof PluginClassLoader)) {
+            if (!(pluginClassLoaderClass.isAssignableFrom(targetLoader.getClass()))) {
                 continue;
             }
             for (Class<?> testClass : classes) {