diff --git a/src/main/java/org/mcphackers/launchwrapper/Launch.java b/src/main/java/org/mcphackers/launchwrapper/Launch.java
index fac5cc8..43eaae5 100644
--- a/src/main/java/org/mcphackers/launchwrapper/Launch.java
+++ b/src/main/java/org/mcphackers/launchwrapper/Launch.java
@@ -9,8 +9,7 @@ public class Launch {
 	 * Class loader where overwritten classes will be stored
 	 */
 	public static final String VERSION = "1.0";
-	@Deprecated
-	public static final LaunchClassLoader CLASS_LOADER = LaunchClassLoader.instantiate();
+	private static final LaunchClassLoader CLASS_LOADER = LaunchClassLoader.instantiate();
 	static {
 		CLASS_LOADER.addException("org.mcphackers.launchwrapper");
 		CLASS_LOADER.addException("org.objectweb.asm");
@@ -31,19 +30,20 @@ public static void main(String[] args) {
 	}
 
 	public void launch() {
-		CLASS_LOADER.setDebugOutput(new java.io.File(config.gameDir.get(), "debug"));
+		LaunchClassLoader loader = getLoader();
 		Tweak mainTweak = getTweak();
 		if(mainTweak == null) {
 			System.err.println("Could not find launch target");
 			return;
 		}
-		if(mainTweak.transform(CLASS_LOADER)) {
-			mainTweak.transformResources(CLASS_LOADER);
+		mainTweak.prepare(loader);
+		if(mainTweak.transform(loader)) {
+			mainTweak.transformResources(loader);
 			if(config.discordRPC.get()) {
 				setupDiscordRPC();
 			}
-			CLASS_LOADER.setLoaderTweak(mainTweak.getLoaderTweak());
-			mainTweak.getLaunchTarget().launch(CLASS_LOADER);
+			loader.setLoaderTweak(mainTweak.getLoaderTweak());
+			mainTweak.getLaunchTarget().launch(loader);
 		} else {
 			System.err.println("Tweak could not be applied");
 		}
diff --git a/src/main/java/org/mcphackers/launchwrapper/loader/LaunchClassLoader.java b/src/main/java/org/mcphackers/launchwrapper/loader/LaunchClassLoader.java
index be097f4..6958d1b 100644
--- a/src/main/java/org/mcphackers/launchwrapper/loader/LaunchClassLoader.java
+++ b/src/main/java/org/mcphackers/launchwrapper/loader/LaunchClassLoader.java
@@ -231,9 +231,10 @@ public void saveDebugClass(ClassNode node) {
 	 */
 	// FIXME require name to contain slashes
 	public ClassNode getClass(String name) {
-		if(classNodeName(name).startsWith("java/")) {
-			return null;
-		}
+		// TODO Breaks SafeClassWriter?
+		// if(classNodeName(name).startsWith("java/")) {
+		// 	return null;
+		// }
 		ClassNode node = classNodeCache.get(classNodeName(name));
 		if(node != null) {
 			return node;
@@ -317,8 +318,10 @@ private Class<?> transformedClass(String name) throws ClassNotFoundException {
 		ClassNode transformed = overridenClasses.get(name);
 		if(transformed != null) {
 			if(tweak != null) {
-				tweak.tweakClass(this, classNodeName(name));
-				transformed = overridenClasses.get(name);
+				if(tweak.tweakClass(this, classNodeName(name))) {
+					transformed = overridenClasses.get(name);
+					saveDebugClass(transformed);
+				}
 			}
 			return redefineClass(transformed);
 		}
diff --git a/src/main/java/org/mcphackers/launchwrapper/tweak/Tweak.java b/src/main/java/org/mcphackers/launchwrapper/tweak/Tweak.java
index f0d0ec1..a96c8a1 100644
--- a/src/main/java/org/mcphackers/launchwrapper/tweak/Tweak.java
+++ b/src/main/java/org/mcphackers/launchwrapper/tweak/Tweak.java
@@ -6,6 +6,7 @@
 
 import org.mcphackers.launchwrapper.LaunchConfig;
 import org.mcphackers.launchwrapper.LaunchTarget;
+import org.mcphackers.launchwrapper.loader.LaunchClassLoader;
 import org.mcphackers.launchwrapper.tweak.injection.Injection;
 import org.mcphackers.launchwrapper.util.ClassNodeSource;
 import org.mcphackers.launchwrapper.util.ResourceSource;
@@ -35,6 +36,10 @@ public Tweak(LaunchConfig config) {
 	
 	public void transformResources(ResourceSource source) {
 	}
+
+	// Any classpath changes required for transformers can be set here
+	public void prepare(LaunchClassLoader loader) {
+	}
 	
 	public final boolean transform(ClassNodeSource source) {
 		if(!clean) {