diff --git a/Hlt/HltServices/src/GitANNSvc.cpp b/Hlt/HltServices/src/GitANNSvc.cpp
index 57dd0085625ba019e05d3ec444045fb8313c93e2..cb8e12e17d1bd182b34bb41719e18fb65cdfb929 100644
--- a/Hlt/HltServices/src/GitANNSvc.cpp
+++ b/Hlt/HltServices/src/GitANNSvc.cpp
@@ -207,7 +207,7 @@ class GitANNSvc : public ANNSvcBase {
       return {};
     }
     lumi_schema_t m;
-    m.size = sz;
+    m.size = sz->template get<unsigned>();
     std::transform( j->begin(), j->end(), std::back_inserter( m.counters ),
                     []( const nlohmann::json& k ) { return IIndexedLumiSchemaSvc::from_json( k ); } );
     return m;