diff --git a/js/common/model/AncillaryTool.ts b/js/common/model/AncillaryTool.ts
index 6b4a7382..9f5429bd 100644
--- a/js/common/model/AncillaryTool.ts
+++ b/js/common/model/AncillaryTool.ts
@@ -163,10 +163,11 @@ export default class AncillaryTool extends PhetioObject {
 
 /**
  * As the xProperty for a curve changes, provide the corresponding CurvePoint.
+ * Note that curve.pointsProperty may also be changed via PhET-iO, see https://github.com/phetsims/calculus-grapher/issues/307.
  * Return type is ReadOnlyProperty so that we can call notifyListenersStatic.
  */
 function createCurvePointProperty( curve: Curve, xProperty: TReadOnlyProperty<number> ): ReadOnlyProperty<CurvePoint> {
-  return new DerivedProperty( [ xProperty ], x => curve.getClosestPointAt( x ) );
+  return new DerivedProperty( [ curve.pointsProperty, xProperty ], ( points, x ) => curve.getClosestPointAt( x ) );
 }
 
 /**
diff --git a/js/common/model/Curve.ts b/js/common/model/Curve.ts
index ab1e2249..1fb76e71 100644
--- a/js/common/model/Curve.ts
+++ b/js/common/model/Curve.ts
@@ -57,7 +57,7 @@ export default class Curve extends PhetioObject {
   // The collection of points that describe the curve. This is an array of CurvePoint instances that are typically
   // mutated in place, so that we have acceptable performance. If Curve was instantiated with pointsPropertyReadOnly:false,
   // then it is possible to set pointsProperty via PhET-iO.
-  private readonly pointsProperty: Property<CurvePoint[]>;
+  public readonly pointsProperty: Property<CurvePoint[]>;
 
   // Using an observable Property for the y-value was considered, but it was deemed to be
   // invasive to the performance of the simulation as observers had to listen to the yProperty