diff --git a/Source/cmVTKMakeInstantiatorCommand.cxx b/Source/cmVTKMakeInstantiatorCommand.cxx
index 0c6c21ae86..2266f8e754 100644
--- a/Source/cmVTKMakeInstantiatorCommand.cxx
+++ b/Source/cmVTKMakeInstantiatorCommand.cxx
@@ -187,7 +187,7 @@ cmVTKMakeInstantiatorCommand
       {
       cmGeneratedFileStream fout(fullName.c_str());
     
-      unsigned int thisBlockSize =
+      size_t thisBlockSize =
         (block < numFullBlocks)? groupSize:lastBlockSize;
     
       // Actually generate the code in the file.