diff --git a/src/libxrpl/protocol/STObject.cpp b/src/libxrpl/protocol/STObject.cpp
index 4b3ace2be3..c2543d2cca 100644
--- a/src/libxrpl/protocol/STObject.cpp
+++ b/src/libxrpl/protocol/STObject.cpp
@@ -899,6 +899,10 @@ STObject::add(Serializer& s, WhichFields whichFields) const
         XRPL_ASSERT(
             (sType != STI_OBJECT) || (field->getFName().fieldType == STI_OBJECT),
             "xrpl::STObject::add : valid field type");
+        XRPL_ASSERT(
+            getStyle(field->getFName()) != SoeDefault || !field->isDefault(),
+            "xrpl::STObject::add : non-default value");
+
         field->addFieldID(s);
         field->add(s);
         if (sType == STI_ARRAY || sType == STI_OBJECT)