diff --git a/Tracking/TrkFitter/TrkGaussianSumFilter/src/MultiComponentStateModeCalculator.cxx b/Tracking/TrkFitter/TrkGaussianSumFilter/src/MultiComponentStateModeCalculator.cxx
index 09bb2cadce6b33d7fe637a0d0ca79503738e9631..6a7df3538a3181e8e1d5a6b71e940b1d7c319e27 100644
--- a/Tracking/TrkFitter/TrkGaussianSumFilter/src/MultiComponentStateModeCalculator.cxx
+++ b/Tracking/TrkFitter/TrkGaussianSumFilter/src/MultiComponentStateModeCalculator.cxx
@@ -15,7 +15,7 @@
 #include "TrkParameters/TrackParameters.h"
 
 namespace {
-constexpr double invsqrt2PI = 1. / sqrt(2. * M_PI);
+const double invsqrt2PI = 1. / sqrt(2. * M_PI);
 
 /** bried method to determine the value of the a gaussian distribution at a
  * given value */