diff --git a/api/services/kb/chunker.py b/api/services/kb/chunker.py
index d416568..42014ad 100644
--- a/api/services/kb/chunker.py
+++ b/api/services/kb/chunker.py
@@ -128,6 +128,10 @@ def _as_dicts(chunks: list[Chunk]) -> list[dict]:
     result: list[dict] = []
     for c in chunks:
         clean, page_in_body = _strip_page_markers(c.content)
+        # _split_oversized may slice a piece in the middle of a marker
+        # sentinel, leaving a stray \x00 that PostgreSQL's UTF-8 check
+        # rejects. Drop any surviving null bytes.
+        clean = clean.replace("\x00", "")
         # Prefer the page the caller computed from the chunk's START offset
         # (the "where does this quote begin" answer). Only fall back to any
         # marker inside the body if the caller didn't set one.