diff --git a/Tracking/TrkFitter/TrkGaussianSumFilter/TrkGaussianSumFilter/IMultiStateExtrapolator.h b/Tracking/TrkFitter/TrkGaussianSumFilter/TrkGaussianSumFilter/IMultiStateExtrapolator.h
index d506e6ae8f1908268d54cbabea2401fcd4ca1ddf..6a33bf2581f06b35791891670d6d0cd858e8246f 100644
--- a/Tracking/TrkFitter/TrkGaussianSumFilter/TrkGaussianSumFilter/IMultiStateExtrapolator.h
+++ b/Tracking/TrkFitter/TrkGaussianSumFilter/TrkGaussianSumFilter/IMultiStateExtrapolator.h
@@ -93,7 +93,7 @@ public:
     //!< Garbage bin for TrackParameter objects
     std::vector<std::unique_ptr<const TrackParameters>> m_tpGarbageBin;
 
-    Cache() { m_materialEffectsCaches.reserve(72); }
+    Cache() { m_materialEffectsCaches.reserve(12); }
 
     void reset()
     {