diff --git a/src/ol/rotationconstraint.js b/src/ol/rotationconstraint.js
index 0f6e3d2dea..fc73600f4e 100644
--- a/src/ol/rotationconstraint.js
+++ b/src/ol/rotationconstraint.js
@@ -10,6 +10,20 @@ goog.require('goog.math');
 ol.RotationConstraintType;
 
 
+/**
+ * @param {number|undefined} rotation Rotation.
+ * @param {number} delta Delta.
+ * @return {number|undefined} Rotation.
+ */
+ol.RotationConstraint.disable = function(rotation, delta) {
+  if (goog.isDef(rotation)) {
+    return 0;
+  } else {
+    return undefined;
+  }
+};
+
+
 /**
  * @param {number|undefined} rotation Rotation.
  * @param {number} delta Delta.