diff --git a/yt/frontends/rockstar/data_structures.py b/yt/frontends/rockstar/data_structures.py
index 3eafc65980..06f71a36d3 100644
--- a/yt/frontends/rockstar/data_structures.py
+++ b/yt/frontends/rockstar/data_structures.py
@@ -59,6 +59,10 @@ def _read_member(
 
         with open(self.filename, "rb") as f:
             f.seek(ipos, os.SEEK_SET)
+            print(
+                f"Reading {self._Npart[ind_halo]} particles for halo {ihalo}. position={f.tell()}"
+            )
+            # assert False
             ids = np.fromfile(f, dtype=np.int64, count=self._Npart[ind_halo])
             return ids