diff --git a/xsdconvert/Mstring.cc b/xsdconvert/Mstring.cc
index e839b7dc7b92cb7ebf37fcd145a67835cb256264..4c020d8bac91614fce28e8a65dfb7eb089669090 100644
--- a/xsdconvert/Mstring.cc
+++ b/xsdconvert/Mstring.cc
@@ -133,7 +133,7 @@ void Mstring::removeWSfromBegin() {
 }
 
 void Mstring::removeWSfromEnd() {
-  int i = mstrlen(text);
+  size_t i = mstrlen(text);
   for (; i > 0; --i)
     if (!isspace((const unsigned char) text[i - 1])) break;
   text = mtruncstr(text, i);