diff --git a/CHANGELOG.md b/CHANGELOG.md
index a8a99dfe3c..8d5bcb382c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,6 +51,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Type inference for Structs with instance methods https://github.com/o1-labs/snarkyjs/pull/567
   - also fixes `Struct.fromJSON`
 - `SmartContract.fetchEvents` fixed when multiple event types existed https://github.com/o1-labs/snarkyjs/issues/627
+- Error when using reduce with a `Struct` as state type https://github.com/o1-labs/snarkyjs/pull/689
 
 ## [0.7.3](https://github.com/o1-labs/snarkyjs/compare/5f20f496...d880bd6e)
 
diff --git a/src/lib/zkapp.ts b/src/lib/zkapp.ts
index b29b17cfba..3588b2395c 100644
--- a/src/lib/zkapp.ts
+++ b/src/lib/zkapp.ts
@@ -1268,16 +1268,8 @@ Use the optional \`maxTransactionsWithActions\` argument to increase this number
         // also, for each action length, compute the new state and then pick the actual one
         let newStates = actionss.map((actions) => {
           // we generate a new witness for the state so that this doesn't break if `apply` modifies the state
-          let newState = Circuit.witness(stateType, () => {
-            // TODO: why doesn't this work without the toConstant mapping?
-            let { toFields, fromFields, toAuxiliary } = stateType;
-            return fromFields(
-              toFields(state).map((x) => x.toConstant()),
-              toAuxiliary(state)
-            );
-            // return state;
-          });
-          Circuit.assertEqual(newState, state);
+          let newState = Circuit.witness(stateType, () => state);
+          Circuit.assertEqual(stateType, newState, state);
           actions.forEach((action) => {
             newState = reduce(newState, action);
           });