diff --git a/fastapi/utils.py b/fastapi/utils.py
index 12eaa2bf0..a43099165 100644
--- a/fastapi/utils.py
+++ b/fastapi/utils.py
@@ -41,7 +41,8 @@ def is_body_allowed_for_status_code(status_code: int | str | None) -> bool:
 
 
 def get_path_param_names(path: str) -> set[str]:
-    return set(re.findall("{(.*?)}", path))
+    params = re.findall("{(.*?)}", path)
+    return {param.split(":", 1)[0] for param in params}
 
 
 _invalid_args_message = (
diff --git a/tests/test_starlette_urlconvertors.py b/tests/test_starlette_urlconvertors.py
index 5ef1b819c..0737b51b9 100644
--- a/tests/test_starlette_urlconvertors.py
+++ b/tests/test_starlette_urlconvertors.py
@@ -19,6 +19,11 @@ def path_convertor(param: str = Path()):
     return {"path": param}
 
 
+@app.get("/path-implicit/{param:path}")
+def path_convertor_implicit(param: str):
+    return {"path": param}
+
+
 @app.get("/query/")
 def query_convertor(param: str = Query()):
     return {"query": param}
@@ -50,6 +55,13 @@ def test_route_converters_path():
     assert response.json() == {"path": "some/example"}
 
 
+def test_route_converters_path_implicit():
+    # Test path conversion without explicit Path()
+    response = client.get("/path-implicit/some/example")
+    assert response.status_code == 200, response.text
+    assert response.json() == {"path": "some/example"}
+
+
 def test_route_converters_query():
     # Test query conversion
     response = client.get("/query", params={"param": "Qué tal!"})