diff --git a/Common/MathUtils/include/MathUtils/SMatrixGPU.h b/Common/MathUtils/include/MathUtils/SMatrixGPU.h
index 60965a4fa2776..6557c92643d44 100644
--- a/Common/MathUtils/include/MathUtils/SMatrixGPU.h
+++ b/Common/MathUtils/include/MathUtils/SMatrixGPU.h
@@ -468,6 +468,12 @@ class SMatrixGPU
   GPUd() const T& operator()(unsigned int i, unsigned int j) const;
   GPUd() T& operator()(unsigned int i, unsigned int j);
 
+  template <typename X>
+  friend X& operator<<(X& x, const SMatrixGPU&)
+  {
+    return x;
+  }
+
   class SMatrixRowGPU
   {
    public:
@@ -512,6 +518,12 @@ class SMatrixGPU
   R mRep;
 };
 
+template <class T, unsigned int D1, unsigned int D2, class R, typename X>
+X& operator<<(X& x, const SMatrixGPU<T, D1, D2, R>&)
+{
+  return x;
+}
+
 template <class T, unsigned int D1, unsigned int D2, class R>
 GPUdi() SMatrixGPU<T, D1, D2, R>::SMatrixGPU(SMatrixIdentity)
 {
diff --git a/GPU/Common/GPUCommonRtypes.h b/GPU/Common/GPUCommonRtypes.h
index 5ae2ddbb83b26..fd7a360bba0d4 100644
--- a/GPU/Common/GPUCommonRtypes.h
+++ b/GPU/Common/GPUCommonRtypes.h
@@ -20,14 +20,13 @@
 #if defined(GPUCA_STANDALONE) || (defined(GPUCA_O2_LIB) && !defined(GPUCA_O2_INTERFACE)) || defined(GPUCA_GPUCODE) // clang-format off
   #if !defined(ROOT_Rtypes) && !defined(__CLING__)
     #define GPUCOMMONRTYPES_H_ACTIVE
+    #define ROOT_Rtypes GPUCommonRtypes_ALREADY_INCLUDED // If you want to use GPUCommonRtypes.h and Rtypes.h in the same file, make sure Rtypes.h is included first!
     #define ClassDef(name,id)
     #define ClassDefNV(name, id)
     #define ClassDefOverride(name, id)
     #define ClassImp(name)
     #define templateClassImp(name)
     #ifndef GPUCA_GPUCODE_DEVICE
-//      typedef uint64_t ULong64_t;
-//      typedef uint32_t UInt_t;
       #include <iostream>
     #endif
   #endif
diff --git a/GPU/Common/GPUROOTSMatrixFwd.h b/GPU/Common/GPUROOTSMatrixFwd.h
index a3b5abc55d3bc..44b2254949df2 100644
--- a/GPU/Common/GPUROOTSMatrixFwd.h
+++ b/GPU/Common/GPUROOTSMatrixFwd.h
@@ -52,7 +52,7 @@ template <class T, uint32_t D1, uint32_t D2>
 class MatRepStdGPU;
 } // namespace detail
 
-#if !defined(GPUCA_STANDALONE) && !defined(GPUCA_GPUCODE)
+#if !defined(GPUCA_STANDALONE) && !defined(GPUCA_GPUCODE) && !defined(GPUCOMMONRTYPES_H_ACTIVE)
 template <typename T, uint32_t N>
 using SVector = ROOT::Math::SVector<T, N>;
 template <class T, uint32_t D1, uint32_t D2, class R>
diff --git a/GPU/GPUTracking/Refit/GPUTrackingRefitKernel.cxx b/GPU/GPUTracking/Refit/GPUTrackingRefitKernel.cxx
index 6baea86f05d36..f7e3bca47a0fc 100644
--- a/GPU/GPUTracking/Refit/GPUTrackingRefitKernel.cxx
+++ b/GPU/GPUTracking/Refit/GPUTrackingRefitKernel.cxx
@@ -12,9 +12,9 @@
 /// \file GPUTrackingRefitKernel.cxx
 /// \author David Rohr
 
+#include "GPUROOTDump.h"
 #include "GPUTrackingRefitKernel.h"
 #include "GPUTrackingRefit.h"
-#include "GPUROOTDump.h"
 
 using namespace GPUCA_NAMESPACE::gpu;