diff --git a/Tracking/TrkVertexFitter/TrkVKalVrtCore/src/VKvFast.cxx b/Tracking/TrkVertexFitter/TrkVKalVrtCore/src/VKvFast.cxx
index aeee7bd4eebc8dca3505253e5d2f145889accd97..d25bb4556d82b20a73d31eb4bc5c99604ecd4b47 100755
--- a/Tracking/TrkVertexFitter/TrkVKalVrtCore/src/VKvFast.cxx
+++ b/Tracking/TrkVertexFitter/TrkVKalVrtCore/src/VKvFast.cxx
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
 
 #include "TrkVKalVrtCore/CommonPars.h"
@@ -18,7 +18,7 @@ namespace Trk {
 
 void vkvfast_(double *p1, double *p2, double *dbmag, double *out)
 {
-    void vkvFastV(double*, double*, double* vRef, double, double *out);
+    double vkvFastV(double*, double*, double* vRef, double, double *out);
     vkvFastV(p1, p2, nullptr, (*dbmag), out);   }