diff --git a/src/borg/cache.py b/src/borg/cache.py
index 2b6082b3a..79c0a4979 100644
--- a/src/borg/cache.py
+++ b/src/borg/cache.py
@@ -15,7 +15,7 @@
 from .helpers import Location
 from .helpers import Error
 from .helpers import get_cache_dir, get_security_dir
-from .helpers import bin_to_hex
+from .helpers import int_to_bigint, bigint_to_int, bin_to_hex
 from .helpers import format_file_size
 from .helpers import safe_ns
 from .helpers import yes
@@ -354,7 +354,7 @@ def commit(self):
                     # this is to avoid issues with filesystem snapshots and mtime granularity.
                     # Also keep files from older backups that have not reached BORG_FILES_CACHE_TTL yet.
                     entry = FileCacheEntry(*msgpack.unpackb(item))
-                    if entry.age == 0 and entry.mtime < self._newest_mtime or \
+                    if entry.age == 0 and bigint_to_int(entry.mtime) < self._newest_mtime or \
                        entry.age > 0 and entry.age < ttl:
                         msgpack.pack((path_hash, entry), fd)
         pi.output('Saving cache config')
@@ -574,7 +574,7 @@ def file_known_and_unchanged(self, path_hash, st, ignore_inode=False):
         if not entry:
             return None
         entry = FileCacheEntry(*msgpack.unpackb(entry))
-        if (entry.size == st.st_size and entry.mtime == st.st_mtime_ns and
+        if (entry.size == st.st_size and bigint_to_int(entry.mtime) == st.st_mtime_ns and
                 (ignore_inode or entry.inode == st.st_ino)):
             # we ignored the inode number in the comparison above or it is still same.
             # if it is still the same, replacing it in the tuple doesn't change it.
@@ -593,6 +593,6 @@ def memorize_file(self, path_hash, st, ids):
         if not (self.do_files and stat.S_ISREG(st.st_mode)):
             return
         mtime_ns = safe_ns(st.st_mtime_ns)
-        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, mtime=mtime_ns, chunk_ids=ids)
+        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, mtime=int_to_bigint(mtime_ns), chunk_ids=ids)
         self.files[path_hash] = msgpack.packb(entry)
         self._newest_mtime = max(self._newest_mtime or 0, mtime_ns)
diff --git a/src/borg/item.pyx b/src/borg/item.pyx
index 627ffd1fb..6404a130d 100644
--- a/src/borg/item.pyx
+++ b/src/borg/item.pyx
@@ -2,6 +2,7 @@ from collections import namedtuple
 
 from .constants import ITEM_KEYS
 from .helpers import safe_encode, safe_decode
+from .helpers import bigint_to_int, int_to_bigint
 from .helpers import StableDict
 
 API_VERSION = '1.1_02'
@@ -156,9 +157,9 @@ class Item(PropDict):
     rdev = PropDict._make_property('rdev', int)
     bsdflags = PropDict._make_property('bsdflags', int)
 
-    atime = PropDict._make_property('atime', int)
-    ctime = PropDict._make_property('ctime', int)
-    mtime = PropDict._make_property('mtime', int)
+    atime = PropDict._make_property('atime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
+    ctime = PropDict._make_property('ctime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
+    mtime = PropDict._make_property('mtime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
 
     # size is only present for items with a chunk list and then it is sum(chunk_sizes)
     # compatibility note: this is a new feature, in old archives size will be missing.
diff --git a/src/borg/testsuite/item.py b/src/borg/testsuite/item.py
index 9c66b6a67..4dedcdc1f 100644
--- a/src/borg/testsuite/item.py
+++ b/src/borg/testsuite/item.py
@@ -77,6 +77,17 @@ def test_item_int_property():
         item.mode = "invalid"
 
 
+def test_item_bigint_property():
+    item = Item()
+    small, big = 42, 2 ** 65
+    item.atime = small
+    assert item.atime == small
+    assert item.as_dict() == {'atime': small}
+    item.atime = big
+    assert item.atime == big
+    assert item.as_dict() == {'atime': b'\0' * 8 + b'\x02'}
+
+
 def test_item_user_group_none():
     item = Item()
     item.user = None