diff --git a/src/ol/proj/proj.js b/src/ol/proj/proj.js
index 5b3bd0b6e8..6b1bbc996d 100644
--- a/src/ol/proj/proj.js
+++ b/src/ol/proj/proj.js
@@ -706,6 +706,7 @@ ol.proj.get = function(projectionLike) {
  * @param {ol.proj.Projection} projection1 Projection 1.
  * @param {ol.proj.Projection} projection2 Projection 2.
  * @return {boolean} Equivalent.
+ * @api
  */
 ol.proj.equivalent = function(projection1, projection2) {
   if (projection1 === projection2) {