diff --git a/test/fiddle/test_function.rb b/test/fiddle/test_function.rb
index c6f78284d5..eb8ef232e8 100644
--- a/test/fiddle/test_function.rb
+++ b/test/fiddle/test_function.rb
@@ -92,7 +92,7 @@ module Fiddle
       n1 = f.call(nil, 0, msec)
       n2 = th.value
       t1 = Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
-      assert_in_delta(msec, t1 - t0, 150, 'slept amount of time')
+      assert_in_delta(msec, t1 - t0, 180, 'slept amount of time')
       assert_equal(0, n1, perror("poll(2) in main-thread"))
       assert_equal(0, n2, perror("poll(2) in sub-thread"))
     end