diff --git a/backend/src/services/martin.rs b/backend/src/services/martin.rs
index 678fe30..067a37c 100644
--- a/backend/src/services/martin.rs
+++ b/backend/src/services/martin.rs
@@ -29,7 +29,13 @@ impl MartinService {
         x: u32,
         y: u32,
     ) -> Result<(Bytes, Option<String>), AppError> {
-        let url = format!("{}/{layer}/{z}/{x}/{y}", self.base_url);
+        // Martin serves composite tiles via comma-separated source names in the URL.
+        let martin_layer = if layer == "osm_all" {
+            "planet_osm_polygon,planet_osm_line,planet_osm_point,planet_osm_roads"
+        } else {
+            layer
+        };
+        let url = format!("{}/{martin_layer}/{z}/{x}/{y}", self.base_url);
         let resp = self.client.get(&url).send().await.map_err(|e| {
             tracing::error!(error = %e, "Martin connection error");
             AppError::ServiceUnavailable("Martin tile server is unreachable".into())