diff --git a/README.md b/README.md
index 49734a34..89afd6a3 100644
--- a/README.md
+++ b/README.md
@@ -149,6 +149,12 @@ package-private.
 Version History
 ---------------
 
+### Upcoming
+
+- Fixed a crash when trying backport classes that are part of the JRE, but
+  the JRE's class differs from the class being backported
+  ([Issue #29](https://github.com/orfjackal/retrolambda/issues/29))
+
 ### Retrolambda 1.6.0 (2014-08-20)
 
 - Does not anymore require the use of a Java agent
diff --git a/end-to-end-tests/src/test/java/com/sun/javafx/application/LauncherImpl.java b/end-to-end-tests/src/test/java/com/sun/javafx/application/LauncherImpl.java
new file mode 100644
index 00000000..73bca7c7
--- /dev/null
+++ b/end-to-end-tests/src/test/java/com/sun/javafx/application/LauncherImpl.java
@@ -0,0 +1,19 @@
+// Copyright © 2013-2014 Esko Luontola <www.orfjackal.net>
+// This software is released under the Apache License 2.0.
+// The license text is at http://www.apache.org/licenses/LICENSE-2.0
+
+package com.sun.javafx.application;
+
+import net.orfjackal.retrolambda.test.ClasspathTest;
+
+/**
+ * @see ClasspathTest#prefers_classes_in_explicit_classpath_over_classes_in_the_JRE
+ */
+@SuppressWarnings("UnusedDeclaration")
+public class LauncherImpl {
+
+    public Runnable foo() {
+        return () -> {
+        };
+    }
+}
diff --git a/end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/ClasspathTest.java b/end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/ClasspathTest.java
index 9e33c5df..876cefff 100644
--- a/end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/ClasspathTest.java
+++ b/end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/ClasspathTest.java
@@ -11,6 +11,7 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertNotNull;
 
 public class ClasspathTest {
 
@@ -45,4 +46,15 @@ public Runnable foo() {
         }
         new RequiresMainClassesInTestClasspath().foo();
     }
+
+    /**
+     * This is to reproduce a bug where trying to backport a development
+     * version of JavaFX classes fails because the same classes also exist in
+     * the JRE's extension directory and Retrolambda accidentally loads the
+     * old built-in class instead of the new class that is being transformed.
+     */
+    @Test
+    public void prefers_classes_in_explicit_classpath_over_classes_in_the_JRE() {
+        assertNotNull(getClass().getResource("/com/sun/javafx/application/LauncherImpl$$Lambda$1.class"));
+    }
 }
diff --git a/retrolambda/src/main/java/net/orfjackal/retrolambda/NonDelegatingClassLoader.java b/retrolambda/src/main/java/net/orfjackal/retrolambda/NonDelegatingClassLoader.java
new file mode 100644
index 00000000..edfc58e4
--- /dev/null
+++ b/retrolambda/src/main/java/net/orfjackal/retrolambda/NonDelegatingClassLoader.java
@@ -0,0 +1,27 @@
+// Copyright © 2013-2014 Esko Luontola <www.orfjackal.net>
+// This software is released under the Apache License 2.0.
+// The license text is at http://www.apache.org/licenses/LICENSE-2.0
+
+package net.orfjackal.retrolambda;
+
+import java.net.*;
+
+public class NonDelegatingClassLoader extends URLClassLoader {
+
+    public NonDelegatingClassLoader(URL[] urls) {
+        super(urls);
+    }
+
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+        Class<?> c = findLoadedClass(name);
+        if (c != null) {
+            return c;
+        }
+        try {
+            return findClass(name);
+        } catch (ClassNotFoundException e) {
+            return super.loadClass(name);
+        }
+    }
+}
diff --git a/retrolambda/src/main/java/net/orfjackal/retrolambda/Retrolambda.java b/retrolambda/src/main/java/net/orfjackal/retrolambda/Retrolambda.java
index 5f2f0de3..06ddc0be 100644
--- a/retrolambda/src/main/java/net/orfjackal/retrolambda/Retrolambda.java
+++ b/retrolambda/src/main/java/net/orfjackal/retrolambda/Retrolambda.java
@@ -30,7 +30,7 @@ public static void run(Config config) throws Throwable {
             return;
         }
 
-        Thread.currentThread().setContextClassLoader(new URLClassLoader(asUrls(classpath)));
+        Thread.currentThread().setContextClassLoader(new NonDelegatingClassLoader(asUrls(classpath)));
 
         try (LambdaClassDumper dumper = new LambdaClassDumper(new LambdaClassSaver(outputDir, bytecodeVersion))) {
             if (!PreMain.isAgentLoaded()) {