diff --git a/pydantic_extra_types/s3.py b/pydantic_extra_types/s3.py
index b58068c..eaf1254 100644
--- a/pydantic_extra_types/s3.py
+++ b/pydantic_extra_types/s3.py
@@ -40,14 +40,16 @@ class TestModel(BaseModel):
     ```
     """
 
-    patt: ClassVar[str] = r'^s3://([^/]+)/(.*?([^/]+)/?)$'
+    patt: ClassVar[re.Pattern[str]] = re.compile(r'^s3://([^/]+)/(.*?([^/]+)/?)$')
 
     def __init__(self, value: str) -> None:
         self.value = value
-        groups: tuple[str, str, str] = re.match(self.patt, self.value).groups()  # type: ignore
-        self.bucket: str = groups[0]
-        self.key: str = groups[1]
-        self.last_key: str = groups[2]
+        match = self.patt.match(self.value)
+        if match is None:
+            raise ValueError(f'Invalid S3 path: {value!r}')
+        self.bucket: str = match.group(1)
+        self.key: str = match.group(2)
+        self.last_key: str = match.group(3)
 
     def __str__(self) -> str:  # pragma: no cover
         return self.value
@@ -65,5 +67,4 @@ def __get_pydantic_core_schema__(cls, source: type[Any], handler: GetCoreSchemaH
         return core_schema.with_info_after_validator_function(
             cls._validate,
             core_schema.str_schema(pattern=cls.patt),
-            field_name=cls.__class__.__name__,
         )
diff --git a/tests/test_s3.py b/tests/test_s3.py
index abfb1e4..c636b0e 100644
--- a/tests/test_s3.py
+++ b/tests/test_s3.py
@@ -150,3 +150,17 @@ def test_s3(raw: str, bucket: str, key: str, last_key: str):
 def test_wrong_s3():
     with pytest.raises(ValidationError):
         S3Check(path='s3/ok')
+
+
+@pytest.mark.parametrize(
+    'invalid_path',
+    [
+        's3/ok',
+        'not-an-s3-path',
+        's3://bucket-only',
+    ],
+)
+def test_wrong_s3_raises_value_error(invalid_path: str):
+    """Test that invalid S3 paths raise ValueError."""
+    with pytest.raises(ValueError, match='Invalid S3 path'):
+        S3Path(invalid_path)