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 33432b14e..25a9f6222 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
@@ -26,7 +26,7 @@ import org.teavm.runtime.Fiber;
 public class TThread extends TObject implements TRunnable {
     private static TThread mainThread = new TThread("main");
     private static TThread currentThread = mainThread;
-    private static long nextId = 1;
+    private static int nextId = 1;
     private static int activeCount = 1;
     private long id;
     private int priority;