diff --git a/graf3d/gl/src/TGLFontManager.cxx b/graf3d/gl/src/TGLFontManager.cxx
index 7142e7568489f..7ffcff5ae8da7 100644
--- a/graf3d/gl/src/TGLFontManager.cxx
+++ b/graf3d/gl/src/TGLFontManager.cxx
@@ -188,6 +188,15 @@ void TGLFont::RenderHelper(const Char *txt, Double_t x, Double_t y, Double_t ang
    glPushMatrix();
    //glLoadIdentity();
 
+   #ifndef BUILTIN_FTGL
+   // https://github.com/root-project/root/issues/22076#issuecomment-4342764706
+      char* vtxt = (char*)txt; // cast away const
+      const auto len = strlen(vtxt);
+      for(auto i = 0UL; i < len; ++i)
+         if (static_cast<unsigned char>(vtxt[i]) > static_cast<unsigned char>('\277'))
+            vtxt[i] = '\277';
+   #endif
+
    // FTGL is not const correct.
    Float_t llx = 0.f, lly = 0.f, llz = 0.f, urx = 0.f, ury = 0.f, urz = 0.f;
    BBox(txt, llx, lly, llz, urx, ury, urz);