diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TThread.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TThread.java
index 1245f6982..33432b14e 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TThread.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TThread.java
@@ -41,10 +41,6 @@ public class TThread extends TObject implements TRunnable {
     private boolean alive = true;
     TRunnable target;
 
-    static {
-        mainThread.setDaemon(true);
-    }
-
     public TThread() {
         this(null, null);
     }
@@ -65,7 +61,11 @@ public class TThread extends TObject implements TRunnable {
 
     public void start() {
         if (PlatformDetector.isLowLevel()) {
-            EventQueue.offer(() -> Fiber.start(this::runThread));
+            boolean daemon = this.daemon;
+            if (!daemon) {
+                Fiber.userThreadCount++;
+            }
+            EventQueue.offer(() -> Fiber.start(this::runThread, daemon));
         } else {
             Platform.startThread(this::runThread);
         }
@@ -207,8 +207,12 @@ public class TThread extends TObject implements TRunnable {
         TThread current = currentThread();
         SleepHandler handler = new SleepHandler(current, callback);
         if (PlatformDetector.isLowLevel()) {
-            handler.scheduleId = EventQueue.offer(handler, System.currentTimeMillis() + millis);
-            current.interruptHandler = handler;
+            if (current.interruptedFlag) {
+                handler.interrupted();
+            } else {
+                handler.scheduleId = EventQueue.offer(handler, System.currentTimeMillis() + millis);
+                current.interruptHandler = handler;
+            }
         } else {
             int intMillis = millis < Integer.MAX_VALUE ? (int) millis : Integer.MAX_VALUE;
             handler.scheduleId = Platform.schedule(handler, intMillis);
diff --git a/core/src/main/java/org/teavm/runtime/Fiber.java b/core/src/main/java/org/teavm/runtime/Fiber.java
index 8cfcea40f..2ed1f3dc9 100644
--- a/core/src/main/java/org/teavm/runtime/Fiber.java
+++ b/core/src/main/java/org/teavm/runtime/Fiber.java
@@ -25,7 +25,7 @@ public class Fiber {
     public static final int STATE_RUNNING = 0;
     public static final int STATE_SUSPENDING = 1;
     public static final int STATE_RESUMING = 2;
-    private static int daemonCount = 1;
+    public static int userThreadCount = 1;
 
     private int[] intValues;
     private int intTop;
@@ -41,11 +41,13 @@ public class Fiber {
     private FiberRunner runner;
     private Object result;
     private Throwable exception;
+    private boolean daemon;
 
     private static Fiber current;
 
-    private Fiber(FiberRunner runner) {
+    private Fiber(FiberRunner runner, boolean daemon) {
         this.runner = runner;
+        this.daemon = daemon;
     }
 
     public void push(int value) {
@@ -207,12 +209,12 @@ public class Fiber {
 
     static native void setCurrentThread(Thread thread);
 
-    public static void start(FiberRunner runner) {
-        new Fiber(runner).start();
+    public static void start(FiberRunner runner, boolean daemon) {
+        new Fiber(runner, daemon).start();
     }
 
     static void startMain() {
-        start(Fiber::runMain);
+        start(Fiber::runMain, false);
     }
 
     static native void runMain();
@@ -222,7 +224,7 @@ public class Fiber {
         current = this;
         runner.run();
         current = former;
-        if (!isSuspending() && Thread.currentThread().isDaemon() && --daemonCount == 0) {
+        if (!isSuspending() && !daemon && --userThreadCount == 0) {
             EventQueue.stop();
         }
     }