diff --git a/controllers/helmrepository_controller.go b/controllers/helmrepository_controller.go
index 725a3079e..f8c7fd210 100644
--- a/controllers/helmrepository_controller.go
+++ b/controllers/helmrepository_controller.go
@@ -255,14 +255,17 @@ func (r *HelmRepositoryReconciler) notify(oldObj, newObj *sourcev1.HelmRepositor
 			sourcev1.GroupVersion.Group + "/checksum": newObj.Status.Artifact.Checksum,
 		}
 
-		size := units.HumanSize(float64(*newObj.Status.Artifact.Size))
+		humanReadableSize := "unknown size"
+		if size := newObj.Status.Artifact.Size; size != nil {
+			humanReadableSize = fmt.Sprintf("size %s", units.HumanSize(float64(*size)))
+		}
 
 		var oldChecksum string
 		if oldObj.GetArtifact() != nil {
 			oldChecksum = oldObj.GetArtifact().Checksum
 		}
 
-		message := fmt.Sprintf("stored fetched index of size %s from '%s'", size, chartRepo.URL)
+		message := fmt.Sprintf("stored fetched index of %s from '%s'", humanReadableSize, chartRepo.URL)
 
 		// Notify on new artifact and failure recovery.
 		if oldChecksum != newObj.GetArtifact().Checksum {
diff --git a/controllers/helmrepository_controller_test.go b/controllers/helmrepository_controller_test.go
index 54171b1cf..7a1e5d593 100644
--- a/controllers/helmrepository_controller_test.go
+++ b/controllers/helmrepository_controller_test.go
@@ -859,6 +859,15 @@ func TestHelmRepositoryReconciler_notify(t *testing.T) {
 			res:    sreconcile.ResultEmpty,
 			resErr: errors.New("some error"),
 		},
+		{
+			name:   "new artifact with nil size",
+			res:    sreconcile.ResultSuccess,
+			resErr: nil,
+			newObjBeforeFunc: func(obj *sourcev1.HelmRepository) {
+				obj.Status.Artifact = &sourcev1.Artifact{Revision: "xxx", Checksum: "yyy", Size: nil}
+			},
+			wantEvent: "Normal NewArtifact stored fetched index of unknown size",
+		},
 		{
 			name:   "new artifact",
 			res:    sreconcile.ResultSuccess,