diff --git a/slsDetectorGui/src/qTabMeasurement.cpp b/slsDetectorGui/src/qTabMeasurement.cpp
index 3e126762b..c2df7922b 100644
--- a/slsDetectorGui/src/qTabMeasurement.cpp
+++ b/slsDetectorGui/src/qTabMeasurement.cpp
@@ -839,7 +839,7 @@ void qTabMeasurement::UpdateProgress() {
 int qTabMeasurement::VerifyOutputDirectoryError() {
     try {
         auto retval = det->getFilePath();
-        for (size_t i = 0; i < retval.size(); i++) {
+        for (int i = 0; i < static_cast<int>(retval.size()); ++i) {
             det->setFilePath(retval[i], {i});
         }
         return slsDetectorDefs::OK;