diff --git a/types/openlayers/index.d.ts b/types/openlayers/index.d.ts
index 79820b98ac..3e151ac32c 100644
--- a/types/openlayers/index.d.ts
+++ b/types/openlayers/index.d.ts
@@ -3970,7 +3970,7 @@ declare module ol {
              * @template T,S
              * @api
              */
-            forEachSegment<T, S>(callback: (() => T), opt_this?: S): (T | boolean);
+            forEachSegment<T, S>(callback: ((this: S, start: ol.Coordinate, end: ol.Coordinate) => T), opt_this?: S): (T | boolean);
 
             /**
              * Returns the coordinate at `m` using linear interpolation, or `null` if no