diff --git a/src/main/scala/org/gerweck/scalafx/util/observable.scala b/src/main/scala/org/gerweck/scalafx/util/observable.scala
index a84156a..fc36bca 100644
--- a/src/main/scala/org/gerweck/scalafx/util/observable.scala
+++ b/src/main/scala/org/gerweck/scalafx/util/observable.scala
@@ -42,6 +42,7 @@ trait ObservableImplicits {
         val newVal = recalculate()
         if (prevValue != newVal) {
           prop.value = newVal
+          prevValue = newVal
         }
       }