Index: lib/dbtexmf/dblatex/grubber/index.py
--- lib/dbtexmf/dblatex/grubber/index.py.orig
+++ lib/dbtexmf/dblatex/grubber/index.py
@@ -351,6 +351,7 @@ class Makeindex:
         msg.debug(" ".join(cmd))
 
         # Makeindex outputs everything to stderr, even progress messages
+        os.environ['TEXMFOUTPUT'] = dirname(self.pbase)
         rc = subprocess.call(cmd, stderr=msg.stdout)
         if (rc != 0):
             msg.error(_("could not make index %s") % self.target)
