diff --git a/rag/retriever/keyword_search.py b/rag/retriever/keyword_search.py
index bad161f..14dbfbb 100644
--- a/rag/retriever/keyword_search.py
+++ b/rag/retriever/keyword_search.py
@@ -21,6 +21,11 @@ def index(self, chunks: list[dict]) -> None:
             chunks: List of chunk dicts with 'text' field
         """
         self.chunks = chunks
+        if not chunks:
+            # BM25Okapi([]) divides by zero in IDF; keep an empty, searchable index.
+            self.bm25 = None
+            logger.info("keyword_index_built", chunk_count=0)
+            return
         tokenized_corpus = [self._tokenize(chunk["text"]) for chunk in chunks]
         self.bm25 = BM25Okapi(tokenized_corpus)
         logger.info("keyword_index_built", chunk_count=len(chunks))
diff --git a/tests/unit/test_keyword_search.py b/tests/unit/test_keyword_search.py
index 6d2d326..a43047f 100644
--- a/tests/unit/test_keyword_search.py
+++ b/tests/unit/test_keyword_search.py
@@ -131,10 +131,6 @@ def test_results_preserve_chunk_fields(self, searcher):
         assert result["source"] == "readme"
         assert result["custom"] == "value"
 
-    @pytest.mark.xfail(
-        strict=True,
-        reason="issue #68 (manifest H-01): BM25 keyword search raises ZeroDivisionError on an empty index",
-    )
     def test_empty_index(self, searcher):
         """Test searching on empty index."""
         searcher.index([])