diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index d26b483..2a58773 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -237,7 +237,7 @@
     _start = XMLUtil::SkipWhiteSpace( _start );
 
     if ( *_start ) {
-        char* p = _start;	// the read pointer
+        const char* p = _start;	// the read pointer
         char* q = _start;	// the write pointer
 
         while( *p ) {
@@ -267,7 +267,7 @@
         _flags ^= NEEDS_FLUSH;
 
         if ( _flags ) {
-            char* p = _start;	// the read pointer
+            const char* p = _start;	// the read pointer
             char* q = _start;	// the write pointer
 
             while( p < _end ) {
diff --git a/tinyxml2.h b/tinyxml2.h
index 05e5cda..4fe2ab5 100755
--- a/tinyxml2.h
+++ b/tinyxml2.h
@@ -139,6 +139,8 @@
     ~StrPair();
 
     void Set( char* start, char* end, int flags ) {
+        TIXMLASSERT( start );
+        TIXMLASSERT( end );
         Reset();
         _start  = start;
         _end    = end;