diff --git a/InnerDetector/InDetValidation/InDetPhysValMonitoring/src/InDetPerfPlot_VertexTruthMatching.cxx b/InnerDetector/InDetValidation/InDetPhysValMonitoring/src/InDetPerfPlot_VertexTruthMatching.cxx
index 6b534cf436f4a8c4ef7b65c95a5119ab3013110f..a6b21a33004b4279d8091b5c4a907d7180763539 100644
--- a/InnerDetector/InDetValidation/InDetPhysValMonitoring/src/InDetPerfPlot_VertexTruthMatching.cxx
+++ b/InnerDetector/InDetValidation/InDetPhysValMonitoring/src/InDetPerfPlot_VertexTruthMatching.cxx
@@ -410,7 +410,7 @@ void InDetPerfPlot_VertexTruthMatching::fill(const xAOD::VertexContainer& vertex
             }
           
             const xAOD::TruthVertex *matchVertex = getTruthVertex(vertex);
-            if(not matchVertex) continue;
+            if(!matchVertex) continue;
             float residual_z = matchVertex->z() - vertex->z();
             float residual_x = matchVertex->x() - vertex->x();
             float residual_y = matchVertex->y() - vertex->y();