patch.diff

diff --git a/core/src/main/java/org/jruby/util/JRubyClassLoader.java b/core/src/main/java/org/jruby/util/JRubyClassLoader.java
index 18c1cc8453..a6326ed6eb 100644
--- a/core/src/main/java/org/jruby/util/JRubyClassLoader.java
+++ b/core/src/main/java/org/jruby/util/JRubyClassLoader.java
@@ -37,6 +37,7 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.lang.management.ManagementFactory;
 import java.net.URL;
+import java.net.URLClassLoader;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -71,7 +72,17 @@ public class JRubyClassLoader extends ClassDefiningJRubyClassLoader {
     private final List<String> cachedJarPaths = Collections.synchronizedList(new ArrayList<String>());
 
     public JRubyClassLoader(ClassLoader parent) {
-        super(parent);
+        super(new DontCloseMeBroClassLoader(parent));
+    }
+
+    private static class DontCloseMeBroClassLoader extends URLClassLoader {
+        public DontCloseMeBroClassLoader(ClassLoader parent) {
+            super(new URL[0], parent);
+        }
+
+        protected void addURL(URL url) {
+            super.addURL(url);
+        }
     }
 
     // Change visibility so others can see it
@@ -103,8 +114,13 @@ public class JRubyClassLoader extends ClassDefiningJRubyClassLoader {
             } catch (IOException e) {
                 throw new RuntimeException("BUG: we can not copy embedded jar to temp directory", e);
             }
+
+            // add temp URLs directly to this classloader, which will be closed
+            super.addURL( url );
+        } else {
+            // add normal paths and other forms to non-closing parent classloader
+            ((DontCloseMeBroClassLoader) getParent()).addURL(url);
         }
-        super.addURL( url );
     }
 
     private static synchronized File getTempDir() {
@@ -171,6 +187,10 @@ public class JRubyClassLoader extends ClassDefiningJRubyClassLoader {
     @Override
     public void close() {
         try {
+            // Close this classloader, which will clean up temp jars.
+            // The parent classloader with other forms of jars remains unclosed, allowing cached JarFile instances to
+            // remain usable.
+            // See https://github.com/jruby/jruby/issues/6218
             super.close();
         }
         catch (Exception ex) { LOG.debug(ex); }