diff --git a/api/lines.go b/api/lines.go
index 079a79e..eecca5a 100644
--- a/api/lines.go
+++ b/api/lines.go
@@ -99,6 +99,13 @@ func convertLineType(old string) string {
 
 func convertCode(t, code string) string {
 	if !strings.HasPrefix(code, "line:IDFM:") {
+		if t == "tram" && !strings.HasPrefix(code, "T") {
+			code = "T" + code
+		}
+		if t == "noctilien" && !strings.HasPrefix(code, "N") {
+			code = "N" + code
+		}
+
 		if len(code) != 6 || !strings.HasPrefix(code, "C") {
 			code = searchLine(t, code)
 		}