diff --git a/src/borg/hashindex.pyx b/src/borg/hashindex.pyx
index 97fc213f10..607d3456e8 100644
--- a/src/borg/hashindex.pyx
+++ b/src/borg/hashindex.pyx
@@ -78,7 +78,8 @@ class ChunkIndex(HTProxyMixin, MutableMapping):
             flags = self.F_USED
         else:
             flags = v.flags | self.F_USED
-            assert v.size == 0 or v.size == size
+            if v.size != 0 and v.size != size:
+                raise ValueError(f"Invalid size: expected 0 or {size}, got {v.size}")
         self[key] = ChunkIndexEntry(flags=flags, size=size)
 
     def __getitem__(self, key):
@@ -217,8 +218,10 @@ class NSIndex1(HTProxyMixin, MutableMapping):
         magic, entries, buckets, ksize, vsize = struct.unpack(self.HEADER_FMT, header_bytes)
         if magic != self.MAGIC:
             raise ValueError(f"Invalid file, magic {self.MAGIC.decode()} not found.")
-        assert ksize == self.KEY_SIZE, "invalid key size"
-        assert vsize == self.VALUE_SIZE, "invalid value size"
+        if ksize != self.KEY_SIZE:
+            raise ValueError("Invalid key size")
+        if vsize != self.VALUE_SIZE:
+            raise ValueError("Invalid value size")
         buckets_size = buckets * (ksize + vsize)
         current_pos = fd.tell()
         end_of_file = fd.seek(0, os.SEEK_END)
@@ -230,4 +233,5 @@ class NSIndex1(HTProxyMixin, MutableMapping):
             value = fd.read(vsize)
             self.ht._set_raw(key, value)
         pos = fd.tell()
-        assert pos == end_of_file
+        if pos != end_of_file:
+            raise ValueError(f"Expected pos ({pos}) to be at end_of_file ({end_of_file})")
diff --git a/src/borg/platform/posix.pyx b/src/borg/platform/posix.pyx
index 84c413701e..0b2e71c018 100644
--- a/src/borg/platform/posix.pyx
+++ b/src/borg/platform/posix.pyx
@@ -44,10 +44,14 @@ def process_alive(host, pid, thread):
     from . import local_pid_alive
     from . import hostid
 
-    assert isinstance(host, str)
-    assert isinstance(hostid, str)
-    assert isinstance(pid, int)
-    assert isinstance(thread, int)
+    if not isinstance(host, str):
+        raise TypeError("host must be a string")
+    if not isinstance(hostid, str):
+        raise TypeError("hostid must be a string")
+    if not isinstance(pid, int):
+        raise TypeError("pid must be an integer")
+    if not isinstance(thread, int):
+        raise TypeError("thread must be an integer")
 
     if host != hostid:
         return True
@@ -116,7 +120,8 @@ def group2gid(group, default=None):
 def posix_acl_use_stored_uid_gid(acl):
     """Replace the user/group field with the stored uid/gid
     """
-    assert isinstance(acl, bytes)
+    if not isinstance(acl, bytes):
+        raise TypeError("acl must be of type bytes")
     from ..helpers import safe_decode, safe_encode
     entries = []
     for entry in safe_decode(acl).split('\n'):