diff --git a/paper-api/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java b/paper-api/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
index 993a8c02af..6bdd9f1dcc 100644
--- a/paper-api/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
+++ b/paper-api/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
@@ -101,7 +101,12 @@ final class PluginClassLoader extends URLClassLoader {
 
     Class<?> loadClass0(@NotNull String name, boolean resolve, boolean checkGlobal, boolean checkLibraries) throws ClassNotFoundException {
         try {
-            return super.loadClass(name, resolve);
+            Class<?> result = super.loadClass(name, resolve);
+
+            // SPIGOT-6749: Library classes will appear in the above, but we don't want to return them to other plugins
+            if (checkGlobal || result.getClassLoader() == this) {
+                return result;
+            }
         } catch (ClassNotFoundException ex) {
         }