diff --git a/glib/gtimer.c b/glib/gtimer.c
index de0ef1b93..e95ac0ead 100644
--- a/glib/gtimer.c
+++ b/glib/gtimer.c
@@ -251,7 +251,8 @@ void
 g_usleep (gulong microseconds)
 {
 #ifdef G_OS_WIN32
-  Sleep (microseconds / 1000);
+  /* Round up to the next millisecond */
+  Sleep (microseconds ? (1 + (microseconds - 1) / 1000) : 0);
 #else
   struct timespec request, remaining;
   request.tv_sec = microseconds / G_USEC_PER_SEC;
diff --git a/gobject/tests/threadtests.c b/gobject/tests/threadtests.c
index b623e8ba4..bb57bd4a8 100644
--- a/gobject/tests/threadtests.c
+++ b/gobject/tests/threadtests.c
@@ -247,6 +247,12 @@ test_threaded_weak_ref (void)
   else
     n = NUM_COUNTER_INCREMENTS / 20;
 
+#ifdef G_OS_WIN32
+  /* On Windows usleep has millisecond resolution and gets rounded up
+   * leading to the test running for a long time. */
+  n /= 10;
+#endif
+
   for (i = 0; i < n; i++)
     {
       UnrefInThreadData data;