diff --git a/packages/state/synchronized.js b/packages/state/synchronized.js
index d42cf4e..2640c25 100644
--- a/packages/state/synchronized.js
+++ b/packages/state/synchronized.js
@@ -84,7 +84,7 @@ export function Synchronized(Superclass) {
     }
 
     tick(elapsed) {
-      for (let i = 0; i < this._childrenWithTickers.length; i++) {
+      for (let i = 0; i < this._childrenWithTickers.length; ++i) {
         const key = this._childrenWithTickers[i];
         this[key].tick(elapsed);
       }
@@ -95,11 +95,11 @@ export function Synchronized(Superclass) {
 
     tickMutateState() {
       this.state = this.state.withMutations((state) => {
-        for (let i = 0; i < this._childrenWithState.length; i++) {
+        for (let i = 0; i < this._childrenWithState.length; ++i) {
           const key = this._childrenWithState[i];
           state.set(key, this[key].state);
         }
-        for (let i = 0; i < this._childrenWithoutState.length; i++) {
+        for (let i = 0; i < this._childrenWithoutState.length; ++i) {
           const key = this._childrenWithoutState[i];
           state.set(key, this[key]);
         }