diff --git a/activesupport/lib/active_support/secure_random.rb b/activesupport/lib/active_support/secure_random.rb
index 688165f9a3fcd..97971e883007e 100644
--- a/activesupport/lib/active_support/secure_random.rb
+++ b/activesupport/lib/active_support/secure_random.rb
@@ -164,13 +164,13 @@ def self.random_number(n=0)
           hex = n.to_s(16)
           hex = '0' + hex if (hex.length & 1) == 1
           bin = [hex].pack("H*")
-          mask = bin[0].ord
+          mask = bin[0]
           mask |= mask >> 1
           mask |= mask >> 2
           mask |= mask >> 4
           begin
             rnd = SecureRandom.random_bytes(bin.length)
-            rnd[0] = (rnd[0].ord & mask).chr
+            rnd[0] = rnd[0] & mask
           end until rnd < bin
           rnd.unpack("H*")[0].hex
         else
diff --git a/activesupport/test/secure_random_test.rb b/activesupport/test/secure_random_test.rb
index b0b6c21a81b4a..44694cd811baf 100644
--- a/activesupport/test/secure_random_test.rb
+++ b/activesupport/test/secure_random_test.rb
@@ -12,4 +12,8 @@ def test_hex
     b2 = ActiveSupport::SecureRandom.hex(64)
     assert_not_equal b1, b2
   end
+
+  def test_random_number
+    assert ActiveSupport::SecureRandom.random_number(5000) < 5000
+  end
 end