diff --git a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
index 7be0f9f3..c174272b 100644
--- a/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
+++ b/packages/squiggle-lang/src/rescript/FunctionRegistry/Library/FR_List.res
@@ -73,19 +73,18 @@ module Internals = {
     accessors: ProjectAccessorsT.t,
     reducer: ProjectReducerFnT.t,
   ) => {
-    let mappedList = aValueArray->Belt.Array.reduceReverse(list{}, (acc, elem) => {
-      let newElem = Reducer_Expression_Lambda.doLambdaCall(
+    Js.Array2.filter(aValueArray, elem => {
+      let result = Reducer_Expression_Lambda.doLambdaCall(
         aLambdaValue,
         list{elem},
         accessors,
         reducer,
       )
-      switch newElem {
-      | IEvBool(true) => list{elem, ...acc}
-      | _ => acc
+      switch result {
+      | IEvBool(true) => true
+      | _ => false
       }
-    })
-    mappedList->Belt.List.toArray->Wrappers.evArray
+    })->Wrappers.evArray
   }
 }