diff --git a/borg/archive.py b/borg/archive.py
index 3cc9c2c22..f676a8473 100644
--- a/borg/archive.py
+++ b/borg/archive.py
@@ -826,7 +826,7 @@ def init_chunks(self):
         """
         # Explicitly set the initial hash table capacity to avoid performance issues
         # due to hash table "resonance"
-        capacity = int(len(self.repository) * 1.2)
+        capacity = int(len(self.repository) * 1.35 + 1)  # > len * 1.0 / HASH_MAX_LOAD (see _hashindex.c)
         self.chunks = ChunkIndex(capacity)
         marker = None
         while True: