diff --git a/activemodel/test/cases/validations/numericality_validation_test.rb b/activemodel/test/cases/validations/numericality_validation_test.rb
index 963ad6450b..8e77a0222e 100644
--- a/activemodel/test/cases/validations/numericality_validation_test.rb
+++ b/activemodel/test/cases/validations/numericality_validation_test.rb
@@ -18,7 +18,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
   FLOATS = [0.0, 10.0, 10.5, -10.5, -0.0001] + FLOAT_STRINGS
   INTEGERS = [0, 10, -10] + INTEGER_STRINGS
   BIGDECIMAL = BIGDECIMAL_STRINGS.collect! { |bd| BigDecimal.new(bd) }
-  JUNK = ["not a number", "42 not a number", "0xdeadbeef", "0xinvalidhex", "00-1", "--3", "+-3", "+3-1", "-+019.0", "12.12.13.12", "123\nnot a number"]
+  JUNK = ["not a number", "42 not a number", "0xdeadbeef", "0xinvalidhex", "0Xdeadbeef", "00-1", "--3", "+-3", "+3-1", "-+019.0", "12.12.13.12", "123\nnot a number"]
   INFINITY = [1.0/0.0]
 
   def test_default_validates_numericality_of