diff --git a/backend/backend/idfm_interface/idfm_interface.py b/backend/backend/idfm_interface/idfm_interface.py
index 99ea17e..82b4316 100644
--- a/backend/backend/idfm_interface/idfm_interface.py
+++ b/backend/backend/idfm_interface/idfm_interface.py
@@ -38,7 +38,6 @@ from .idfm_types import (
 from .ratp_types import Picto as RatpPicto
 
 
-
 logger = getLogger(__name__)
 
 
@@ -60,7 +59,7 @@ class IdfmInterface:
     )
 
     OPERATOR_RE = re_compile(r"[^:]+:Operator::([^:]+):")
-    LINE_RE = re_compile(r"[^:]+:Line::([^:]+):")
+    LINE_RE = re_compile(r"[^:]+:Line::C([^:]+):")
 
     def __init__(self, api_key: str, database: Database) -> None:
         self._api_key = api_key
diff --git a/backend/main.py b/backend/main.py
index e5a1f08..80d615b 100755
--- a/backend/main.py
+++ b/backend/main.py
@@ -199,11 +199,12 @@ async def get_next_passages(stop_id: int) -> NextPassagesSchema | None:
 
             # re.match will return None if the given journey.LineRef.value is not valid.
             try:
-                line_id = IdfmInterface.LINE_RE.match(journey.LineRef.value).group(1)
-            except AttributeError as exc:
+                line_id_match = IdfmInterface.LINE_RE.match(journey.LineRef.value)
+                line_id = int(line_id_match.group(1))  # type: ignore
+            except (AttributeError, TypeError, ValueError) as err:
                 raise HTTPException(
                     status_code=404, detail=f'Line "{journey.LineRef.value}" not found'
-                ) from exc
+                ) from err
 
             call = journey.MonitoredCall