diff --git a/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/ReduceAction.kt b/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/ReduceAction.kt
index 3e1ec62f..99da6cd2 100644
--- a/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/ReduceAction.kt
+++ b/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/actions/ReduceAction.kt
@@ -19,14 +19,14 @@ public class JoinGroup<T : Any, R : Any>(
 
     public var meta: MutableMeta = MutableMeta()
 
-    public lateinit var result: suspend ActionEnv.(Map<Name, T>) -> R
+    public lateinit var result: suspend ActionEnv.(Map<Name, Pair<Meta, T>>) -> R
 
-    internal fun <R1 : R> result(outputType: KType, f: suspend ActionEnv.(Map<Name, T>) -> R1) {
+    internal fun <R1 : R> result(outputType: KType, f: suspend ActionEnv.(Map<Name,  Pair<Meta, T>>) -> R1) {
         this.outputType = outputType
         this.result = f;
     }
 
-    public inline fun <reified R1 : R> result(noinline f: suspend ActionEnv.(Map<Name, T>) -> R1) {
+    public inline fun <reified R1 : R> result(noinline f: suspend ActionEnv.(Map<Name,  Pair<Meta, T>>) -> R1) {
         outputType = typeOf<R1>()
         this.result = f;
     }
@@ -66,7 +66,7 @@ public class ReduceGroupBuilder<T : Any, R : Any>(
     /**
      * Apply transformation to the whole node
      */
-    public fun result(resultName: String, f: suspend ActionEnv.(Map<Name, T>) -> R) {
+    public fun result(resultName: String, f: suspend ActionEnv.(Map<Name,  Pair<Meta, T>>) -> R) {
         groupRules += { node ->
             listOf(JoinGroup<T, R>(resultName, node, outputType).apply { result(outputType, f) })
         }
@@ -82,7 +82,7 @@ internal class ReduceAction<T : Any, R : Any>(
     outputType: KType,
     private val action: ReduceGroupBuilder<T, R>.() -> Unit,
 ) : CachingAction<T, R>(outputType) {
-    //TODO optimize reduction. Currently the whole action recalculates on push
+    //TODO optimize reduction. Currently, the whole action recalculates on push
 
 
     override fun transform(set: DataSet<T>, meta: Meta, key: Name): Sequence<NamedData<R>> = sequence {
diff --git a/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/data/dataTransform.kt b/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/data/dataTransform.kt
index b4e58c2d..aba33561 100644
--- a/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/data/dataTransform.kt
+++ b/dataforge-data/src/commonMain/kotlin/space/kscience/dataforge/data/dataTransform.kt
@@ -49,13 +49,13 @@ public inline fun <T1 : Any, T2 : Any, reified R : Any> Data<T1>.combine(
 public inline fun <T : Any, reified R : Any> Collection<Data<T>>.reduceToData(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
     meta: Meta = Meta.EMPTY,
-    crossinline block: suspend (Collection<T>) -> R,
+    crossinline block: suspend (List<Pair<Meta, T>>) -> R,
 ): Data<R> = Data(
     meta,
     coroutineContext,
     this
 ) {
-    block(map { it.await() })
+    block(map { it.meta to it.await() })
 }
 
 @DFInternal
@@ -63,14 +63,14 @@ public fun <K, T : Any, R : Any> Map<K, Data<T>>.reduceToData(
     outputType: KType,
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
     meta: Meta = Meta.EMPTY,
-    block: suspend (Map<K, T>) -> R,
+    block: suspend (Map<K, Pair<Meta, T>>) -> R,
 ): Data<R> = Data(
     outputType,
     meta,
     coroutineContext,
     this.values
 ) {
-    block(mapValues { it.value.await() })
+    block(mapValues { it.value.meta to it.value.await() })
 }