diff --git a/lib/has_details.rb b/lib/has_details.rb
index 4ac1978..75675a3 100644
--- a/lib/has_details.rb
+++ b/lib/has_details.rb
@@ -52,7 +52,7 @@ def has_details(options = {})
         elsif t == Integer
           "val = (val.nil? ? nil : (Integer(val) rescue nil))"
         elsif t == BigDecimal
-          "val = val.is_a?(BigDecimal) ? val : val.to_d"
+          "val = val.is_a?(BigDecimal) ? val : (val.blank? ? nil : val.to_d)"
         else
           "raise \"Assigned value must be a #{t.inspect}\" unless val.nil? || val.is_a?(#{t.inspect})"
         end