diff --git a/classpath/java/lang/Thread.java b/classpath/java/lang/Thread.java
index 539a709169..936351c809 100644
--- a/classpath/java/lang/Thread.java
+++ b/classpath/java/lang/Thread.java
@@ -156,6 +156,10 @@ public class Thread implements Runnable {
   }
 
   public static void sleep(long milliseconds) throws InterruptedException {
+    if (milliseconds <= 0) {
+      milliseconds = 1;
+    }
+
     Thread t = currentThread();
     if (t.sleepLock == null) {
       t.sleepLock = new Object();
diff --git a/src/classpath-openjdk.cpp b/src/classpath-openjdk.cpp
index b0e0c51a2c..a965fd676d 100644
--- a/src/classpath-openjdk.cpp
+++ b/src/classpath-openjdk.cpp
@@ -3309,6 +3309,10 @@ jvmSleep(Thread* t, uintptr_t* arguments)
 {
   jlong milliseconds; memcpy(&milliseconds, arguments, sizeof(jlong));
 
+  if (milliseconds <= 0) {
+    milliseconds = 1;
+  }
+
   if (threadSleepLock(t, t->javaThread) == 0) {
     object lock = makeJobject(t);
     set(t, t->javaThread, ThreadSleepLock, lock);