Fix regression.

lib/interpol/endpoint.rb

@@ -282,7 +282,7 @@ def conditionally_make_nullable(raw_schema)
       # Mark as non-nullable so it doesn't try to recurse down into it
       # and make it nullable at that level (since we are taking care of it at this level)
       sub_schema = raw_schema.merge('nullable' => false)
-      raw_schema.replace('type' => ['null', sub_schema])
+      raw_schema.replace('type' => ['null', sub_schema], 'optional' => sub_schema['optional'])
     end
 
     def should_be_nullable?(raw_schema)

spec/unit/interpol/endpoint_spec.rb

@@ -397,6 +397,11 @@ def new_with(hash)
         subject.validate_data!({})
       end
 
+      it 'does not require optional nullable properties' do
+        schema['properties']['foo'].merge!('optional' => true, 'nullable' => true)
+        subject.validate_data!({})
+      end
+
       it 'does not allow additional properties' do
         expect {
           subject.validate_data!('bar' => 3)