diff --git a/Source/cmQtAutomoc.cxx b/Source/cmQtAutomoc.cxx
index e5dc3df62..ff96e5b9f 100644
--- a/Source/cmQtAutomoc.cxx
+++ b/Source/cmQtAutomoc.cxx
@@ -519,7 +519,7 @@ void cmQtAutomoc::ParseCppFile(const std::string& absFilename,
   const std::string absPath = cmsys::SystemTools::GetFilenamePath(
                    cmsys::SystemTools::GetRealPath(absFilename.c_str())) + '/';
 
-  long matchOffset = 0;
+  std::string::size_type matchOffset = 0;
   if (!mocIncludeRegExp.find(contentsString.c_str()))
     {
     // no moc #include, look whether we need to create a moc from