diff --git a/tools/src/cti2ctml.cpp b/tools/src/cti2ctml.cpp
index 7392d66c1..8b53015d9 100644
--- a/tools/src/cti2ctml.cpp
+++ b/tools/src/cti2ctml.cpp
@@ -48,7 +48,7 @@ int main(int argc, char** argv) {
       for (int j = 1; j < argc; j++) {
 	tok = string(argv[j]);
 	if (tok[0] == '-') {
-	  int nopt = tok.size();
+	  int nopt = static_cast<int>(tok.size());
 	  for (int n = 1; n < nopt; n++) {
 	    if (tok[n] == 'h') {
 	      printUsage();