diff --git a/geom/gdml/src/TGDMLParse.cxx b/geom/gdml/src/TGDMLParse.cxx
index 9e8ed2453520c..dec02cf7126ef 100644
--- a/geom/gdml/src/TGDMLParse.cxx
+++ b/geom/gdml/src/TGDMLParse.cxx
@@ -99,7 +99,6 @@ When most solids or volumes are added to the geometry they
 #include "TGeoXtru.h"
 #include "TGeoScaledShape.h"
 #include "TGeoTessellated.h"
-#include "TROOT.h"
 #include "TMath.h"
 #include "TMap.h"
 #include "TObjString.h"
@@ -114,7 +113,7 @@ When most solids or volumes are added to the geometry they
 #include "TGeoOpticalSurface.h"
 #include "TGeoSystemOfUnits.h"
 
-#include <stdlib.h>
+#include <cstdlib>
 #include <string>
 #include <sstream>
 #include <locale>
diff --git a/geom/gdml/src/TGDMLWrite.cxx b/geom/gdml/src/TGDMLWrite.cxx
index bc597663b3fe8..82d1aeb332d1e 100644
--- a/geom/gdml/src/TGDMLWrite.cxx
+++ b/geom/gdml/src/TGDMLWrite.cxx
@@ -150,7 +150,6 @@ See that function for details.
 #include "TGeoEltu.h"
 #include "TGeoXtru.h"
 #include "TGeoScaledShape.h"
-#include "TROOT.h"
 #include "TMath.h"
 #include "TGeoBoolNode.h"
 #include "TGeoMedium.h"
@@ -158,7 +157,7 @@ See that function for details.
 #include "TGeoShape.h"
 #include "TGeoCompositeShape.h"
 #include "TGeoOpticalSurface.h"
-#include <stdlib.h>
+#include <cstdlib>
 #include <string>
 #include <map>
 #include <set>
@@ -167,7 +166,7 @@ See that function for details.
 
 ClassImp(TGDMLWrite);
 
-TGDMLWrite *TGDMLWrite::fgGDMLWrite = 0;
+TGDMLWrite *TGDMLWrite::fgGDMLWrite = nullptr;
 
 namespace {
   struct MaterialExtractor  {