diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index ea8088c..510fc82 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -177,6 +177,7 @@ void StrPair::Reset()
 
 void StrPair::SetStr( const char* str, int flags )
 {
+    TIXMLASSERT( str );
     Reset();
     size_t len = strlen( str );
     TIXMLASSERT( _start == 0 );