diff --git a/polyline/polyline.d.ts b/polyline/polyline.d.ts
index 78fb292d1..17389ed7e 100644
--- a/polyline/polyline.d.ts
+++ b/polyline/polyline.d.ts
@@ -8,7 +8,7 @@
 interface Polyline {
   decode(string: string, precision?: number): number[][];
   encode(coordinate: number[][], precision?: number): string;
-  fromGeoJSON(geojson: GeoJSON.LineString | GeoJSON.Feature, precision?: number): string;
+  fromGeoJSON(geojson: GeoJSON.LineString | GeoJSON.Feature<GeoJSON.LineString>, precision?: number): string;
 }
 
 declare var polyline: Polyline;