diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index ca616456f1..4be2cfeeda 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -898,7 +898,7 @@ class TestFloat < Test::Unit::TestCase
       a = rand
       b = a+rand*1000
       s = (b - a) / 10
-      b = a + s*10
+      b = a + s*9.999999
       seq = (a...b).step(s)
       assert_equal(10, seq.to_a.length, seq.inspect)
     end