diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
index 0dfa8531..347f3f0e 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
@@ -105,7 +105,7 @@ internal class EvaluationSessionImpl private constructor (
                 ?.also { it.updateIndexFromRules(program.rules()) }
                 ?: RuleIndex(program.rules())
 
-            val journal = MatchJournalImpl(incrementality)
+            val journal = MatchJournalImpl(incrementality, trace)
             val logicalState = LogicalState()
             val dispatchingFront = Dispatcher(ruleIndex).front()
 
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/MatchJournalImpl.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/MatchJournalImpl.kt
index b13266c2..2c23fdb2 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/MatchJournalImpl.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/MatchJournalImpl.kt
@@ -175,6 +175,27 @@ internal open class MatchJournalImpl(
         return added
     }
 
+    internal fun resetOccurrences(occSpecs: List<Chunk.Entry>) =
+    // assume occSpecs are ordered in order of processing
+        //  so, iterate over reversed list
+        occSpecs.asReversed().forEach {
+            if (it.discarded) {
+
+                trace.undoDiscard(it.occ)
+
+                it.occ.alive = true
+                it.occ.stored = true
+
+            } else {
+
+                trace.undoActivate(it.occ)
+
+                it.occ.alive = false
+                it.occ.stored = false
+            }
+        }
+
+
     override fun initialChunk(): MatchChunk = initialChunk
 
     override fun parentChunk(): MatchChunk = ancestorChunksStack.peek()!!
@@ -379,19 +400,6 @@ internal fun RuleMatch.collectJustifications(vararg withEvidence: Evidence): Jus
         this.allHeads().forEach { allJss.addAll(it.justifications()) }
     }
 
-internal fun resetOccurrences(occSpecs: List<Chunk.Entry>) =
-    // assume occSpecs are ordered in order of processing
-    //  so, iterate over reversed list
-    occSpecs.asReversed().forEach {
-        if (it.discarded) {
-            it.occ.alive = true
-            it.occ.stored = true
-        } else {
-            it.occ.alive = false
-            it.occ.stored = false
-        }
-    }
-
 internal fun <E> MutableList<E>.push(element: E) = this.add(element)
 internal fun <E> MutableList<E>.pop() = this.removeAt(this.size - 1)
 internal fun <E> MutableList<E>.peek() = this.last()
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/evaluation/EvaluationTrace.java b/reactor/Core/src/jetbrains/mps/logic/reactor/evaluation/EvaluationTrace.java
index c562aad1..903aa67d 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/evaluation/EvaluationTrace.java
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/evaluation/EvaluationTrace.java
@@ -31,6 +31,8 @@ public interface EvaluationTrace {
 
     default void activate(ConstraintOccurrence occurrence) {}
 
+    default void undoActivate(ConstraintOccurrence occurrence) {}
+
     default void reactivate(ConstraintOccurrence occurrence) {}
 
     default void activateContinue(ConstraintOccurrence occurrence) {}
@@ -39,6 +41,8 @@ public interface EvaluationTrace {
 
     default void discard(ConstraintOccurrence occurrence) {}
 
+    default void undoDiscard(ConstraintOccurrence occurrence) {}
+
     default void trying(RuleMatch ruleMatch) {}
 
     default void reject(RuleMatch ruleMatch) {}