diff --git a/haystack/components/query/query_expander.py b/haystack/components/query/query_expander.py
index 5279db12abe..2cac9ac07f2 100644
--- a/haystack/components/query/query_expander.py
+++ b/haystack/components/query/query_expander.py
@@ -198,11 +198,11 @@ def run(self, query: str, n_expansions: int | None = None) -> dict[str, list[str
 
         self.warm_up()
 
-        response = {"queries": [query] if self.include_original_query else []}
-
-        if not query.strip():
+        if not isinstance(query, str) or not query.strip():
             logger.warning("Empty query provided to QueryExpander")
-            return response
+            return {"queries": [query] if self.include_original_query and isinstance(query, str) else []}
+
+        response = {"queries": [query] if self.include_original_query else []}
 
         expansion_count = n_expansions if n_expansions is not None else self.n_expansions
         if expansion_count <= 0:
@@ -268,11 +268,11 @@ async def run_async(self, query: str, n_expansions: int | None = None) -> dict[s
 
         await self.warm_up_async()
 
-        response = {"queries": [query] if self.include_original_query else []}
-
-        if not query.strip():
+        if not isinstance(query, str) or not query.strip():
             logger.warning("Empty query provided to QueryExpander")
-            return response
+            return {"queries": [query] if self.include_original_query and isinstance(query, str) else []}
+
+        response = {"queries": [query] if self.include_original_query else []}
 
         expansion_count = n_expansions if n_expansions is not None else self.n_expansions
         if expansion_count <= 0:
diff --git a/releasenotes/notes/fix-query-expander-none-query-b7d4e12c90a5f618.yaml b/releasenotes/notes/fix-query-expander-none-query-b7d4e12c90a5f618.yaml
new file mode 100644
index 00000000000..3b69beb9da1
--- /dev/null
+++ b/releasenotes/notes/fix-query-expander-none-query-b7d4e12c90a5f618.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    ``QueryExpander`` now returns an empty query list when ``query`` is ``None`` or not a string,
+    instead of raising ``AttributeError`` on ``str.strip``.
diff --git a/test/components/query/test_query_expander.py b/test/components/query/test_query_expander.py
index c932f6af257..951369b8a7b 100644
--- a/test/components/query/test_query_expander.py
+++ b/test/components/query/test_query_expander.py
@@ -134,6 +134,20 @@ def test_run_whitespace_only_query(self, monkeypatch, caplog):
         assert result["queries"] == ["\t\n  \r"]
         assert "Empty query provided" in caplog.text
 
+    def test_run_none_query(self, monkeypatch, caplog):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-key-12345")
+        expander = QueryExpander()
+        with caplog.at_level(logging.WARNING):
+            result = expander.run(None)  # type: ignore[arg-type]
+        assert result["queries"] == []
+        assert "Empty query provided" in caplog.text
+
+    def test_run_none_query_include_original(self, monkeypatch):
+        monkeypatch.setenv("OPENAI_API_KEY", "test-key-12345")
+        expander = QueryExpander(include_original_query=False)
+        result = expander.run(None)  # type: ignore[arg-type]
+        assert result["queries"] == []
+
     def test_run_generator_no_replies(self, mock_chat_generator):
         mock_chat_generator.run.return_value = {"replies": []}
         expander = QueryExpander(chat_generator=mock_chat_generator)