diff --git a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlMat.cxx b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlMat.cxx
index de0f80878f92a27be907b169b46ced71b65d97bf..637ce03ef5008cc490aa14504410224aa2b7fa02 100644
--- a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlMat.cxx
+++ b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlMat.cxx
@@ -49,7 +49,7 @@ AlMat::AlMat(const AlMat& m) {
 }
 
 AlMat::~AlMat()
-{if( m_ptr_data != NULL) delete [] m_ptr_data;}
+{if( m_ptr_data != nullptr ) delete [] m_ptr_data;}
 
 void AlMat::copy(const AlMat&  m) {
   int  nr = nrow();
diff --git a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSpaMat.cxx b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSpaMat.cxx
index 144e7388f6d17f2c735101caab0b6c2a13d4aead..8a77e110fc64848c68990abc2033e1f21186c1cd 100644
--- a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSpaMat.cxx
+++ b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSpaMat.cxx
@@ -36,8 +36,8 @@ AlSpaMat::AlSpaMat()
   m_matrix_type = 2;
   m_size = 0;
   m_nele = 0;
-  m_ptr_row = NULL;
-  m_ptr_col = NULL;    // set pointer to null
+  m_ptr_row = nullptr;
+  m_ptr_col = nullptr;    // set pointer to null
 }
 
 //______________________________________________________________________________
@@ -46,8 +46,8 @@ AlSpaMat::AlSpaMat(long int N)
   m_matrix_type = 2;
   m_size = N;
   m_nele = 0;
-  m_ptr_row = NULL;
-  m_ptr_col = NULL;    // set pointer to null
+  m_ptr_row = nullptr;
+  m_ptr_col = nullptr;    // set pointer to null
 }
 
 //______________________________________________________________________________
@@ -56,8 +56,8 @@ AlSpaMat::AlSpaMat(const AlSpaMat& m)
 {
   m_matrix_type = 2;
   m_size = m.size();
-  m_ptr_row = NULL;
-  m_ptr_col = NULL;    // set pointer to null
+  m_ptr_row = nullptr;
+  m_ptr_col = nullptr;    // set pointer to null
   copy(m);
 }
 
@@ -66,8 +66,8 @@ AlSpaMat::AlSpaMat(const AlSymMat& m)
 {
   m_matrix_type = 2;
   m_size = m.size();
-  m_ptr_row = NULL;
-  m_ptr_col = NULL;    // set pointer to null
+  m_ptr_row = nullptr;
+  m_ptr_col = nullptr;    // set pointer to null
   copy(m);
 }
 
@@ -75,8 +75,8 @@ AlSpaMat::AlSpaMat(const AlSymMat& m)
 AlSpaMat::~AlSpaMat()
 {
   m_ptr_map.clear();
-  if( m_ptr_row != NULL )  delete [] m_ptr_row;
-  if( m_ptr_col != NULL )  delete [] m_ptr_col;
+  if( m_ptr_row != nullptr )  delete [] m_ptr_row;
+  if( m_ptr_col != nullptr )  delete [] m_ptr_col;
 }
 
 //______________________________________________________________________________
diff --git a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSymMat.cxx b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSymMat.cxx
index b2a63571fe288fa3ae40711c10e5685cb10d7d69..09dc446a568b43ed88353f495f13a726c788f585 100644
--- a/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSymMat.cxx
+++ b/Tracking/TrkAlignment/TrkAlgebraUtils/src/AlSymMat.cxx
@@ -41,7 +41,7 @@ AlSymMat::AlSymMat()
   m_matrix_type = 1;
   m_size = 0;
   m_nele = 0;
-  m_ptr_data = NULL;  // set pointer to null
+  m_ptr_data = nullptr;  // set pointer to null
   m_pathbin="./";
   m_pathtxt="./";
 }
@@ -105,7 +105,7 @@ AlSymMat& AlSymMat::operator=(const AlSpaMat& m)
 //______________________________________________________________________________
 AlSymMat::~AlSymMat()
 {
-  if( m_ptr_data != NULL ) delete [] m_ptr_data;
+  if( m_ptr_data != nullptr ) delete [] m_ptr_data;
   //ptr_map.clear();
 }