diff --git a/src/ripple/module/app/tx/TransactionMeta.cpp b/src/ripple/module/app/tx/TransactionMeta.cpp
index b07cb12b6d..c5b2331eca 100644
--- a/src/ripple/module/app/tx/TransactionMeta.cpp
+++ b/src/ripple/module/app/tx/TransactionMeta.cpp
@@ -27,7 +27,7 @@ TransactionMetaSet::TransactionMetaSet (uint256 const& txid, std::uint32_t ledge
     Serializer s (vec);
     SerializerIterator sit (s);
 
-    std::unique_ptr<SerializedType> pobj = STObject::deserialize (sit, sfAffectedNodes);
+    std::unique_ptr<SerializedType> pobj = STObject::deserialize (sit, sfMetadata);
     STObject* obj = static_cast<STObject*> (pobj.get ());
 
     if (!obj)
diff --git a/src/ripple/module/data/protocol/FieldNames.cpp b/src/ripple/module/data/protocol/FieldNames.cpp
index 2a3abe2873..eef059f89d 100644
--- a/src/ripple/module/data/protocol/FieldNames.cpp
+++ b/src/ripple/module/data/protocol/FieldNames.cpp
@@ -31,14 +31,15 @@ SField::StaticLockType& SField::getMutex ()
     return mutex;
 }
 
-const SField sfInvalid (-1), sfGeneric (0);
-const SField sfLedgerEntry (STI_LEDGERENTRY, 1, "LedgerEntry");
-const SField sfTransaction (STI_TRANSACTION, 1, "Transaction");
-const SField sfValidation (STI_VALIDATION, 1, "Validation");
-const SField sfHash (STI_HASH256, 257, "hash");
-const SField sfIndex (STI_HASH256, 258, "index");
+SField const sfInvalid (-1), sfGeneric (0);
+SField const sfLedgerEntry (STI_LEDGERENTRY, 257, "LedgerEntry");
+SField const sfTransaction (STI_TRANSACTION, 257, "Transaction");
+SField const sfValidation (STI_VALIDATION, 257, "Validation");
+SField const sfMetadata (STI_METADATA, 257, "Metadata");
+SField const sfHash (STI_HASH256, 257, "hash");
+SField const sfIndex (STI_HASH256, 258, "index");
 
-// TODO(tom): Remove this horrorr.
+// TODO(tom): Remove this horror.
 #define FIELD(name, type, index) \
     SField sf##name(FIELD_CODE(STI_##type, index), STI_##type, index, #name);
 #define TYPE(name, type, index)
diff --git a/src/ripple/module/data/protocol/FieldNames.h b/src/ripple/module/data/protocol/FieldNames.h
index e0e782edca..07731dd4ad 100644
--- a/src/ripple/module/data/protocol/FieldNames.h
+++ b/src/ripple/module/data/protocol/FieldNames.h
@@ -41,9 +41,11 @@ enum SerializedTypeID
 #undef FIELD
 
     // high level types
+    // cannot be serialized inside other types
     STI_TRANSACTION = 10001,
     STI_LEDGERENTRY = 10002,
     STI_VALIDATION  = 10003,
+    STI_METADATA    = 10004,
 };
 
 /** Identifies fields.
@@ -239,8 +241,9 @@ protected:
     SField (SerializedTypeID id, int val);
 };
 
-extern const SField sfInvalid, sfGeneric, sfLedgerEntry, sfTransaction,
-    sfValidation;
+extern const SField
+    sfInvalid, sfGeneric,
+    sfLedgerEntry, sfTransaction, sfValidation, sfMetadata;
 
 #define FIELD(name, type, index) extern SField sf##name;
 #define TYPE(name, type, index)
diff --git a/src/ripple/module/data/protocol/STParsedJSON.cpp b/src/ripple/module/data/protocol/STParsedJSON.cpp
index 7c68c78acb..ff8ecb8dc1 100644
--- a/src/ripple/module/data/protocol/STParsedJSON.cpp
+++ b/src/ripple/module/data/protocol/STParsedJSON.cpp
@@ -705,7 +705,7 @@ bool STParsedJSON::parse (std::string const& json_name,
                             "[" << i << "]." << objectName;
                         bool const success (parse (ss.str (), objectFields,
                             nameField, depth + 1, sub_object_));
-                        if (! success)
+                        if (! success || (sub_object_->getFName().fieldType != STI_OBJECT))
                             return false;
                     }
                     tail->push_back (*sub_object_);
diff --git a/src/ripple/module/data/protocol/SerializedObject.cpp b/src/ripple/module/data/protocol/SerializedObject.cpp
index ea0d1fb123..598c63daba 100644
--- a/src/ripple/module/data/protocol/SerializedObject.cpp
+++ b/src/ripple/module/data/protocol/SerializedObject.cpp
@@ -275,6 +275,12 @@ bool STObject::set (SerializerIterator& sit, int depth)
 
         reachedEndOfObject = (type == STI_OBJECT) && (field == 1);
 
+        if ((type == STI_ARRAY) && (field == 1))
+        {
+            WriteLog (lsWARNING, STObject) << "Encountered object with end of array marker";
+            throw std::runtime_error ("Illegal terminator in object");
+        }
+
         if (!reachedEndOfObject)
         {
             // Figure out the field
@@ -359,6 +365,12 @@ void STObject::add (Serializer& s, bool withSigningFields) const
         // insert them in sorted order
         const SerializedType* field = it.second;
 
+        // When we serialize an object inside another object,
+        // the type associated by rule with this field name
+        // must be OBJECT, or the object cannot be deserialized
+        assert ((field->getSType() != STI_OBJECT) ||
+            (field->getFName().fieldType == STI_OBJECT));
+
         field->addFieldID (s);
         field->add (s);
 
@@ -1215,6 +1227,12 @@ STArray* STArray::construct (SerializerIterator& sit, SField::ref field)
         if ((type == STI_ARRAY) && (field == 1))
             break;
 
+        if ((type == STI_OBJECT) && (field == 1))
+        {
+            WriteLog (lsWARNING, STObject) << "Encountered array with end of object marker";
+            throw std::runtime_error ("Illegal terminator in array");
+        }
+
         SField::ref fn = SField::getField (type, field);
 
         if (fn.isInvalid ())
@@ -1223,6 +1241,12 @@ STArray* STArray::construct (SerializerIterator& sit, SField::ref field)
             throw std::runtime_error ("Unknown field");
         }
 
+        if (fn.fieldType != STI_OBJECT)
+        {
+            WriteLog (lsTRACE, STObject) << "Array contains non-object";
+            throw std::runtime_error ("Non-object in array");
+        }
+
         value.push_back (new STObject (fn));
         value.rbegin ()->set (sit, 1);
     }
diff --git a/src/ripple/module/data/protocol/SerializedTypes.cpp b/src/ripple/module/data/protocol/SerializedTypes.cpp
index cec276c39f..4f1965f94f 100644
--- a/src/ripple/module/data/protocol/SerializedTypes.cpp
+++ b/src/ripple/module/data/protocol/SerializedTypes.cpp
@@ -317,6 +317,8 @@ STVector256* STVector256::construct (SerializerIterator& u, SField::ref name)
 
 void STVector256::add (Serializer& s) const
 {
+    assert (fName->isBinary ());
+    assert (fName->fieldType == STI_VECTOR256);
     s.addVL (mValue.empty () ? nullptr : mValue[0].begin (), mValue.size () * (256 / 8));
 }
 
@@ -542,6 +544,8 @@ std::string STPathSet::getText () const
 
 void STPathSet::add (Serializer& s) const
 {
+    assert (fName->isBinary ());
+    assert (fName->fieldType == STI_PATHSET);
     bool bFirst = true;
 
     BOOST_FOREACH (const STPath & spPath, value)
diff --git a/src/ripple/module/data/protocol/SerializedTypes.h b/src/ripple/module/data/protocol/SerializedTypes.h
index 18dea8df15..1372efee2f 100644
--- a/src/ripple/module/data/protocol/SerializedTypes.h
+++ b/src/ripple/module/data/protocol/SerializedTypes.h
@@ -123,13 +123,14 @@ public:
 
     virtual void add (Serializer& s) const
     {
-        ;
+        assert (false);
     }
 
     virtual bool isEquivalent (const SerializedType& t) const;
 
     void addFieldID (Serializer& s) const
     {
+        assert (fName->isBinary ());
         s.addFieldID (fName->fieldType, fName->fieldValue);
     }
 
@@ -224,6 +225,8 @@ public:
     Json::Value getJson (int) const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_UINT8);
         s.add8 (value);
     }
 
@@ -283,6 +286,8 @@ public:
     Json::Value getJson (int) const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_UINT16);
         s.add16 (value);
     }
 
@@ -342,6 +347,8 @@ public:
     Json::Value getJson (int) const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_UINT32);
         s.add32 (value);
     }
 
@@ -400,6 +407,8 @@ public:
     Json::Value getJson (int) const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_UINT64);
         s.add64 (value);
     }
 
@@ -873,6 +882,8 @@ public:
     virtual std::string getText () const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_HASH128);
         s.add128 (value);
     }
 
@@ -946,6 +957,8 @@ public:
     virtual std::string getText () const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_HASH160);
         s.add160 (value);
     }
 
@@ -1021,6 +1034,8 @@ public:
     std::string getText () const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert (fName->fieldType == STI_HASH256);
         s.add256 (value);
     }
 
@@ -1088,6 +1103,9 @@ public:
     virtual std::string getText () const;
     void add (Serializer& s) const
     {
+        assert (fName->isBinary ());
+        assert ((fName->fieldType == STI_VL) ||
+            (fName->fieldType == STI_ACCOUNT));
         s.addVL (value);
     }