diff --git a/RTCP/Cobalt/CoInterface/src/LTAFeedback.h b/RTCP/Cobalt/CoInterface/src/LTAFeedback.h
index 47f1f1a5814c8c2ea2cc140d162085abdd5ed2ea..d9c621133a8a21a3f1365706e1a280cf39b6e8ca 100644
--- a/RTCP/Cobalt/CoInterface/src/LTAFeedback.h
+++ b/RTCP/Cobalt/CoInterface/src/LTAFeedback.h
@@ -63,8 +63,8 @@ namespace LOFAR
       static const int major_version = 3;
       static const int minor_version = 1;
       static const int patch_number = 0;
-      std::string feedback_version = (boost::format("%02d.%02d.%02d") %
-                                        major_version % minor_version % patch_number).str();
+      static const std::string feedback_version(boost::str(boost::format("%02d.%02d.%02d") %
+                                        major_version % minor_version % patch_number)));
 
     private:
       const ObservationSettings settings;