diff --git a/taglib/toolkit/tstring.cpp b/taglib/toolkit/tstring.cpp
index 168f9f15..e3320951 100644
--- a/taglib/toolkit/tstring.cpp
+++ b/taglib/toolkit/tstring.cpp
@@ -546,7 +546,7 @@ String String::number(int n) // static
   if(negative)
     s += '-';
 
-  for(size_t i = charStack.d->data.size() - 1; i >= 0; i--)
+  for(int i = charStack.d->data.size() - 1; i >= 0; i--)
     s += charStack.d->data[i];
 
   return s;