diff --git a/src/classes/PMusrWebCanvas.cpp b/src/classes/PMusrWebCanvas.cpp
index 1ad17884..58de4655 100644
--- a/src/classes/PMusrWebCanvas.cpp
+++ b/src/classes/PMusrWebCanvas.cpp
@@ -43,6 +43,7 @@
 #include <TROOT.h>
 #include <TStyle.h>
 #include <TSystem.h>
+#include <TVirtualX.h>
 
 #include "PMusrWebCanvas.h"
 
@@ -173,6 +174,33 @@ std::string FindWebDir()
   return std::string();
 }
 
+//------------------------------------------------------------------------
+/**
+ * <p>Puts ROOT into the state a genuine batch session has, and restores the
+ * previous state when it goes out of scope: gROOT's batch flag plus the
+ * graphics interface, see PMusrWebCanvas::RenderGraphics() for why both are
+ * needed.
+ */
+//------------------------------------------------------------------------
+class PBatchGraphicsGuard {
+  public:
+    PBatchGraphicsGuard() : fWasBatch(gROOT->IsBatch()), fSavedVirtualX(gVirtualX) {
+      gROOT->SetBatch(kTRUE);
+      if (gGXBatch != nullptr)
+        gVirtualX = gGXBatch;
+    }
+    ~PBatchGraphicsGuard() {
+      gVirtualX = fSavedVirtualX;
+      gROOT->SetBatch(fWasBatch);
+    }
+    PBatchGraphicsGuard(const PBatchGraphicsGuard &) = delete;
+    PBatchGraphicsGuard &operator=(const PBatchGraphicsGuard &) = delete;
+
+  private:
+    Bool_t fWasBatch;
+    TVirtualX *fSavedVirtualX;
+};
+
 } // anonymous namespace
 
 //--------------------------------------------------------------------------
@@ -1117,8 +1145,24 @@ Bool_t PMusrWebCanvas::RenderGraphics(const std::string &fileName, const PanelVi
   // function is safe here because this canvas is the only one that ever
   // exists in the process: the interactive display never builds a TCanvas of
   // its own (see the class comment above).
-  const Bool_t wasBatch = gROOT->IsBatch();
-  gROOT->SetBatch(kTRUE);
+  //
+  // The batch flag alone is not enough though. An interactive musrview is a
+  // *non-batch* ROOT session, hence TApplication has loaded the X11 graphics
+  // and gVirtualX points at TGX11. A batch TCanvas never obtains a drawable
+  // (its fPixmapID stays -1), yet TCanvas::Build() unconditionally does
+  //
+  //   GetCanvasPainter()->SelectDrawable(fPixmapID);
+  //   PaintBorder(GetFillColor(), kTRUE);
+  //
+  // to paint the canvas background. With the batch gVirtualX that is a no-op,
+  // with TGX11 it selects window -1 and the following TGX11::DrawBoxW()
+  // segfaults. So the graphics interface has to be put into the same state a
+  // genuine batch session has, which is what gGXBatch is: the TVirtualX
+  // instance ROOT installs when it starts up without graphics.
+  //
+  // The guard is declared before the canvas on purpose: it has to outlive it,
+  // since the TCanvas destructor uses the graphics interface as well.
+  PBatchGraphicsGuard batchGuard;
 
   std::string name = "musrviewBatch" + std::to_string(fPlotNumber);
   TCanvas canvas(name.c_str(), fTitle.c_str(), exportWidth, exportHeight);
@@ -1193,10 +1237,8 @@ Bool_t PMusrWebCanvas::RenderGraphics(const std::string &fileName, const PanelVi
     infoPad->Draw();
   }
 
-  if (!FillPlotPad(&dataTheoryPad)) {
-    gROOT->SetBatch(wasBatch);
+  if (!FillPlotPad(&dataTheoryPad))
     return false;
-  }
 
   dataTheoryPad.Update();
   canvas.cd();
@@ -1209,8 +1251,6 @@ Bool_t PMusrWebCanvas::RenderGraphics(const std::string &fileName, const PanelVi
   dataTheoryPad.GetListOfPrimitives()->Clear();
   canvas.GetListOfPrimitives()->Clear();
 
-  gROOT->SetBatch(wasBatch);
-
   return true;
 }