diff --git a/externs/olx.js b/externs/olx.js
index 770eee4abf..4bc33d3092 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -5,21 +5,6 @@
 let olx;
 
 
-/**
- * @typedef {{altitudeMode: (IGCZ|string|undefined)}}
- */
-olx.format.IGCOptions;
-
-
-/**
- * Altitude mode. Possible values are `barometric`, `gps`, and `none`. Default
- * is `none`.
- * @type {IGCZ|string|undefined}
- * @api
- */
-olx.format.IGCOptions.prototype.altitudeMode;
-
-
 /**
  * @typedef {{extractStyles: (boolean|undefined),
  *     defaultStyle: (Array.<ol.style.Style>|undefined),
diff --git a/externs/xol.js b/externs/xol.js
index db6c04be00..9806e8f51f 100644
--- a/externs/xol.js
+++ b/externs/xol.js
@@ -1,11 +1,4 @@
 
-/**
- * @typedef {Object} format_IGCOptions
- * @property {IGCZ|string|undefined} altitudeMode Altitude mode. Possible values are `barometric`, `gps`, and `none`. Default
- * is `none`.
- */
-
-
 /**
  * @typedef {Object} format_KMLOptions
  * @property {boolean|undefined} extractStyles Extract styles from the KML. Default is `true`.
diff --git a/src/ol/format/IGC.js b/src/ol/format/IGC.js
index b4b493958e..ab0a1edac7 100644
--- a/src/ol/format/IGC.js
+++ b/src/ol/format/IGC.js
@@ -19,13 +19,22 @@ const IGCZ = {
   NONE: 'none'
 };
 
+
+/**
+ * @typedef {Object} Options
+ * @property {IGCZ|string|undefined} altitudeMode Altitude mode. Possible
+ * values are `'barometric'`, `'gps'`, and `'none'`. Default
+ * is `'none'`.
+ */
+
+
 /**
  * @classdesc
  * Feature format for `*.igc` flight recording files.
  *
  * @constructor
  * @extends {ol.format.TextFeature}
- * @param {olx.format.IGCOptions=} opt_options Options.
+ * @param {module:ol/format/IGC~Options=} opt_options Options.
  * @api
  */
 const IGC = function(opt_options) {