diff --git a/rtengine/imagedata.cc b/rtengine/imagedata.cc
index dc837117d..f8e257ddc 100644
--- a/rtengine/imagedata.cc
+++ b/rtengine/imagedata.cc
@@ -446,7 +446,7 @@ void ImageData::extractInfo ()
                         if (baseIsoTag) {
                             std::string isoData = baseIsoTag->valueToString();
                             if (isoData.size() > 1) {
-                                iso_speed = atoi(isoData.c_str());
+                                iso_speed = stoi(isoData);
                             }
                         }
                     }