diff --git a/bincio/render/merge.py b/bincio/render/merge.py
index 34c5db4..3d056f3 100644
--- a/bincio/render/merge.py
+++ b/bincio/render/merge.py
@@ -326,7 +326,7 @@ def _merge_all_locked(data_dir: Path) -> int:
     athlete_dest = merged_dir / "athlete.json"
     if athlete_dest.exists() or athlete_dest.is_symlink():
         athlete_dest.unlink()
-    if athlete_src.exists():
+    if athlete_src.exists() and athlete_src.stat().st_size > 0:
         athlete_edits_path = data_dir / "edits" / "athlete.yaml"
         if athlete_edits_path.exists():
             try:
@@ -338,9 +338,12 @@ def _merge_all_locked(data_dir: Path) -> int:
             edits = {}
         _ATHLETE_EDITABLE = {"max_hr", "ftp_w", "hr_zones", "power_zones", "seasons", "gear"}
         if edits:
-            athlete_data = json.loads(athlete_src.read_text(encoding="utf-8"))
-            athlete_data.update({k: v for k, v in edits.items() if k in _ATHLETE_EDITABLE})
-            athlete_dest.write_text(_dumps(athlete_data))
+            try:
+                athlete_data = json.loads(athlete_src.read_text(encoding="utf-8"))
+                athlete_data.update({k: v for k, v in edits.items() if k in _ATHLETE_EDITABLE})
+                athlete_dest.write_text(_dumps(athlete_data))
+            except (json.JSONDecodeError, OSError):
+                pass
         else:
             athlete_dest.symlink_to(athlete_src.resolve())