diff --git a/src/rodwriter.hh b/src/rodwriter.hh
index 2365d7bdbe707238ccb62be5fa2f7fbcc113cffd..a89af411c0981f45d180c3cd19f75d108c77c12f 100644
--- a/src/rodwriter.hh
+++ b/src/rodwriter.hh
@@ -122,7 +122,7 @@ void writeRod(const std::vector<Configuration>& rod,
     // ///////////////////////////////////////
     outfile << "@1" << std::endl;
 
-    for (int i=0; i<rod.size(); i++)
+    for (size_t i=0; i<rod.size(); i++)
         //outfile << rod[i].r[0] << "  " << rod[i].r[1] << "  " << rod[i].r[2] << std::endl;
         outfile << rod[i].r << std::endl;
 
@@ -132,12 +132,12 @@ void writeRod(const std::vector<Configuration>& rod,
     // ///////////////////////////////////////
     outfile << std::endl << "@2" << std::endl;
 
-    for (int i=0; i<rod.size(); i++) 
+    for (size_t i=0; i<rod.size(); i++) 
         outfile << rod[i].q.director(0) << std::endl;
 
     outfile << std::endl << "@3" << std::endl;
 
-    for (int i=0; i<rod.size(); i++) 
+    for (size_t i=0; i<rod.size(); i++) 
         outfile << rod[i].q.director(1) << std::endl;