diff --git a/src/main/java/me/topchetoeu/jscript/repl/debug/DebugServer.java b/src/main/java/me/topchetoeu/jscript/repl/debug/DebugServer.java
index 92fa9a2..718b00b 100644
--- a/src/main/java/me/topchetoeu/jscript/repl/debug/DebugServer.java
+++ b/src/main/java/me/topchetoeu/jscript/repl/debug/DebugServer.java
@@ -63,8 +63,6 @@ public class DebugServer {
 				return;
 			}
 
-			System.out.println(msg);
-
 			switch (msg.name) {
 				case "Debugger.enable":
 					synchronized (connNotifier) {
@@ -140,10 +138,7 @@ public class DebugServer {
 		}
 
 		runAsync(() -> {
-			var handle = new Thread(() -> {
-				System.out.println("test");
-				debugger.close();
-			});
+			var handle = new Thread(debugger::close);
 
 			Runtime.getRuntime().addShutdownHook(handle);
 
diff --git a/src/main/java/me/topchetoeu/jscript/repl/debug/SimpleDebugger.java b/src/main/java/me/topchetoeu/jscript/repl/debug/SimpleDebugger.java
index d1dca69..7b34330 100644
--- a/src/main/java/me/topchetoeu/jscript/repl/debug/SimpleDebugger.java
+++ b/src/main/java/me/topchetoeu/jscript/repl/debug/SimpleDebugger.java
@@ -955,6 +955,7 @@ public class SimpleDebugger implements Debugger {
 
 				obj = proto;
 				own = false;
+				break;
 			}
 		}
 
@@ -1015,7 +1016,7 @@ public class SimpleDebugger implements Debugger {
 		ws.send(msg.respond());
 	}
 
-	@Override public void onSourceLoad(Filename filename, String source) {
+	@Override public synchronized void onSourceLoad(Filename filename, String source) {
 		int id = nextId();
 		var src = new DebugSource(id, filename, source);
 
@@ -1025,7 +1026,7 @@ public class SimpleDebugger implements Debugger {
 		if (!enabled) pendingSources.add(src);
 		else sendSource(src);
 	}
-	@Override public void onFunctionLoad(FunctionBody body, FunctionMap map) {
+	@Override public synchronized void onFunctionLoad(FunctionBody body, FunctionMap map) {
 		for (var bpt : idToBreakpoint.values()) {
 			bpt.addFunc(body, map);
 		}
@@ -1120,7 +1121,7 @@ public class SimpleDebugger implements Debugger {
 
 		return false;
 	}
-	@Override public void onFramePush(Environment env, Frame frame) {
+	@Override public synchronized void onFramePush(Environment env, Frame frame) {
 		var prevFrame = currFrame;
 		updateFrames(env, 0);
 
@@ -1128,7 +1129,7 @@ public class SimpleDebugger implements Debugger {
 			stepOutFrame = currFrame;
 		}
 	}
-	@Override public void onFramePop(Environment env, Frame frame) {
+	@Override public synchronized void onFramePop(Environment env, Frame frame) {
 		updateFrames(env, 1);
 
 		try { idToFrame.remove(codeFrameToFrame.remove(frame).id); }
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/debug/DebugContext.java b/src/main/java/me/topchetoeu/jscript/runtime/debug/DebugContext.java
index 0431cff..860f8bb 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/debug/DebugContext.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/debug/DebugContext.java
@@ -23,7 +23,7 @@ public class DebugContext {
 	private WeakHashMap<FunctionBody, FunctionMap> maps;
 	private DebugHandler debugger;
 
-	public boolean attachDebugger(DebugHandler debugger) {
+	public synchronized boolean attachDebugger(DebugHandler debugger) {
 		if (this.debugger != null) return false;
 
 		if (sources != null) {