diff --git a/playwright/_impl/_assertions.py b/playwright/_impl/_assertions.py
index ce8d63816..2c895e527 100644
--- a/playwright/_impl/_assertions.py
+++ b/playwright/_impl/_assertions.py
@@ -18,6 +18,7 @@
 
 from playwright._impl._api_structures import ExpectedTextValue, FrameExpectOptions
 from playwright._impl._connection import format_call_log
+from playwright._impl._errors import Error
 from playwright._impl._fetch import APIResponse
 from playwright._impl._helper import is_textual_mime_type
 from playwright._impl._locator import Locator
@@ -793,4 +794,6 @@ def to_expected_text_values(
             out.append(
                 expected_regex(item, match_substring, normalize_white_space, ignoreCase)
             )
+        else:
+            raise Error("value must be a string or regular expression")
     return out
diff --git a/tests/async/test_assertions.py b/tests/async/test_assertions.py
index 49b860309..774d60de5 100644
--- a/tests/async/test_assertions.py
+++ b/tests/async/test_assertions.py
@@ -96,6 +96,13 @@ async def test_assertions_locator_to_contain_text(page: Page, server: Server) ->
     await expect(page.locator("div")).to_contain_text(["ext     1", re.compile("ext3")])
 
 
+async def test_assertions_locator_to_contain_text_should_throw_if_arg_is_unsupported_type(
+    page: Page,
+) -> None:
+    with pytest.raises(Error, match="value must be a string or regular expression"):
+        await expect(page.locator("div")).to_contain_text(1)  # type: ignore
+
+
 async def test_assertions_locator_to_have_attribute(page: Page, server: Server) -> None:
     await page.goto(server.EMPTY_PAGE)
     await page.set_content("<div id=foobar>kek</div>")