diff --git a/src/ArcherContainer.js b/src/ArcherContainer.js
index ffa8c28..2174249 100644
--- a/src/ArcherContainer.js
+++ b/src/ArcherContainer.js
@@ -198,7 +198,9 @@ export class ArcherContainer extends React.Component<Props, State> {
 
   unregisterChild = (id: string): void => {
     this.setState((currentState: State) => {
-      currentState.observer.unobserve(currentState.refs[id]);
+      if (currentState.refs[id]) {
+        currentState.observer.unobserve(currentState.refs[id]);
+      }
       const newRefs = { ...currentState.refs };
       delete newRefs[id];
       return { refs: newRefs };