diff --git a/activesupport/lib/active_support/number_helper/number_converter.rb b/activesupport/lib/active_support/number_helper/number_converter.rb
index 22b4a936d1d47..fdcced24d9fbb 100644
--- a/activesupport/lib/active_support/number_helper/number_converter.rb
+++ b/activesupport/lib/active_support/number_helper/number_converter.rb
@@ -179,8 +179,10 @@ def valid_bigdecimal
           case number
           when Float, Rational
             number.to_d(0)
-          else
+          when String
             BigDecimal(number, exception: false)
+          else
+            number.to_d rescue nil
           end
         end
     end
diff --git a/activesupport/test/number_helper_test.rb b/activesupport/test/number_helper_test.rb
index 37272ee19d7ce..a1633ba87b204 100644
--- a/activesupport/test/number_helper_test.rb
+++ b/activesupport/test/number_helper_test.rb
@@ -15,6 +15,16 @@ class TestClassWithClassNumberHelpers
         extend ActiveSupport::NumberHelper
       end
 
+      class NumberWithToD
+        def initialize(number)
+          @number = number
+        end
+
+        def to_d
+          @number.to_d
+        end
+      end
+
       def setup
         @instance_with_helpers = TestClassWithInstanceNumberHelpers.new
       end
@@ -95,6 +105,7 @@ def test_number_to_currency
           assert_equal("-$,11", number_helper.number_to_currency("-,11"))
           assert_equal("$0.00", number_helper.number_to_currency(-0.0))
           assert_equal("$0.00", number_helper.number_to_currency("-0.0"))
+          assert_equal("$1.23", number_helper.number_to_currency(NumberWithToD.new(1.23)))
         end
       end