diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index fc746de..6248f2c 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -623,6 +623,7 @@
 void XMLNode::DeleteChildren()
 {
     while( _firstChild ) {
+        TIXMLASSERT( _firstChild->_document == _document );
         XMLNode* node = _firstChild;
         Unlink( node );
 
@@ -634,6 +635,7 @@
 
 void XMLNode::Unlink( XMLNode* child )
 {
+    TIXMLASSERT( child->_document == _document );
     if ( child == _firstChild ) {
         _firstChild = _firstChild->_next;
     }
@@ -653,6 +655,7 @@
 
 void XMLNode::DeleteChild( XMLNode* node )
 {
+    TIXMLASSERT( node->_document == _document );
     TIXMLASSERT( node->_parent == this );
     DeleteNode( node );
 }
@@ -660,8 +663,10 @@
 
 XMLNode* XMLNode::InsertEndChild( XMLNode* addThis )
 {
-	if (addThis->_document != _document)
-		return 0;
+    if ( addThis->_document != _document ) {
+        TIXMLASSERT( false );
+        return 0;
+    }
 
 	if (addThis->_parent)
 		addThis->_parent->Unlink( addThis );
@@ -691,8 +696,10 @@
 
 XMLNode* XMLNode::InsertFirstChild( XMLNode* addThis )
 {
-	if (addThis->_document != _document)
-		return 0;
+    if ( addThis->_document != _document ) {
+        TIXMLASSERT( false );
+        return 0;
+    }
 
 	if (addThis->_parent)
 		addThis->_parent->Unlink( addThis );
@@ -723,12 +730,16 @@
 
 XMLNode* XMLNode::InsertAfterChild( XMLNode* afterThis, XMLNode* addThis )
 {
-	if (addThis->_document != _document)
-		return 0;
+    TIXMLASSERT( addThis );
+    if ( addThis->_document != _document ) {
+        TIXMLASSERT( false );
+        return 0;
+    }
 
-    TIXMLASSERT( afterThis->_parent == this );
+    TIXMLASSERT( afterThis );
 
     if ( afterThis->_parent != this ) {
+        TIXMLASSERT( false );
         return 0;
     }
 
@@ -944,6 +955,7 @@
 
 bool XMLText::Accept( XMLVisitor* visitor ) const
 {
+    TIXMLASSERT( visitor );
     return visitor->Visit( *this );
 }
 
@@ -984,6 +996,7 @@
 
 bool XMLComment::ShallowEqual( const XMLNode* compare ) const
 {
+    TIXMLASSERT( compare );
     const XMLComment* comment = compare->ToComment();
     return ( comment && XMLUtil::StringEqual( comment->Value(), Value() ));
 }
@@ -991,6 +1004,7 @@
 
 bool XMLComment::Accept( XMLVisitor* visitor ) const
 {
+    TIXMLASSERT( visitor );
     return visitor->Visit( *this );
 }
 
@@ -1032,6 +1046,7 @@
 
 bool XMLDeclaration::ShallowEqual( const XMLNode* compare ) const
 {
+    TIXMLASSERT( compare );
     const XMLDeclaration* declaration = compare->ToDeclaration();
     return ( declaration && XMLUtil::StringEqual( declaration->Value(), Value() ));
 }
@@ -1040,6 +1055,7 @@
 
 bool XMLDeclaration::Accept( XMLVisitor* visitor ) const
 {
+    TIXMLASSERT( visitor );
     return visitor->Visit( *this );
 }
 
@@ -1080,6 +1096,7 @@
 
 bool XMLUnknown::ShallowEqual( const XMLNode* compare ) const
 {
+    TIXMLASSERT( compare );
     const XMLUnknown* unknown = compare->ToUnknown();
     return ( unknown && XMLUtil::StringEqual( unknown->Value(), Value() ));
 }
@@ -1087,6 +1104,7 @@
 
 bool XMLUnknown::Accept( XMLVisitor* visitor ) const
 {
+    TIXMLASSERT( visitor );
     return visitor->Visit( *this );
 }
 
@@ -1556,6 +1574,7 @@
 
 bool XMLElement::ShallowEqual( const XMLNode* compare ) const
 {
+    TIXMLASSERT( compare );
     const XMLElement* other = compare->ToElement();
     if ( other && XMLUtil::StringEqual( other->Value(), Value() )) {
 
@@ -1581,6 +1600,7 @@
 
 bool XMLElement::Accept( XMLVisitor* visitor ) const
 {
+    TIXMLASSERT( visitor );
     if ( visitor->VisitEnter( *this, _rootAttribute ) ) {
         for ( const XMLNode* node=FirstChild(); node; node=node->NextSibling() ) {
             if ( !node->Accept( visitor ) ) {
@@ -1717,6 +1737,8 @@
 
 static FILE* callfopen( const char* filepath, const char* mode )
 {
+    TIXMLASSERT( filepath );
+    TIXMLASSERT( mode );
 #if defined(_MSC_VER) && (_MSC_VER >= 1400 ) && (!defined WINCE)
     FILE* fp = 0;
     errno_t err = fopen_s( &fp, filepath, mode );