diff --git a/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticIndex.java b/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticIndex.java
index b99888127..016ba9054 100644
--- a/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticIndex.java
+++ b/core/src/main/java/art/arcane/iris/world/history/GenerationSemanticIndex.java
@@ -1075,7 +1075,11 @@ public final class GenerationSemanticIndex {
 
     private void cacheRegion(long regionKey, RegionShard region) {
         regions.put(regionKey, region);
-        cacheSummary(regionKey, region.summary());
+        if (region.summary == null) {
+            summaries.remove(regionKey);
+        } else {
+            cacheSummary(regionKey, region.summary);
+        }
         while (regions.size() > MAXIMUM_CACHED_REGIONS) {
             Iterator<Map.Entry<Long, RegionShard>> entries = regions.entrySet().iterator();
             entries.next();
diff --git a/core/src/test/java/art/arcane/iris/world/history/GenerationSemanticIndexTest.java b/core/src/test/java/art/arcane/iris/world/history/GenerationSemanticIndexTest.java
index 08770aa91..27f92bd5e 100644
--- a/core/src/test/java/art/arcane/iris/world/history/GenerationSemanticIndexTest.java
+++ b/core/src/test/java/art/arcane/iris/world/history/GenerationSemanticIndexTest.java
@@ -206,6 +206,27 @@ public final class GenerationSemanticIndexTest {
                 new ChunkGenerationSemantics.BlockPosition(-520, 80, -8), 4)).isEmpty());
     }
 
+    @Test
+    public void claimsDeferRegionSummariesUntilAQueryReadsThem() throws Exception {
+        Path root = temporaryFolder.newFolder("lazy-summaries").toPath();
+        GenerationSemanticIndex index = GenerationSemanticIndex.initialize(root);
+
+        index.claimAndPersist(ChunkGenerationSemantics.builder(-33, -1, 1L).addObject("iris:first").seal().build());
+        assertEquals(0, index.cachedSummaryCount());
+        assertEquals("iris:first", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:first").key());
+        assertEquals(1, index.cachedSummaryCount());
+
+        index.claimAndPersist(ChunkGenerationSemantics.builder(-34, -1, 1L).addObject("iris:second").seal().build());
+        assertEquals(0, index.cachedSummaryCount());
+        assertEquals("iris:second", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:second").key());
+        assertEquals("iris:first", requiredMatch(index, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:first").key());
+        assertEquals(2, sealedClaims(index, 1L).size());
+
+        GenerationSemanticIndex reopened = GenerationSemanticIndex.load(root);
+        assertEquals("iris:second", requiredMatch(reopened, GenerationSemanticIndex.SemanticKind.OBJECT, "iris:second").key());
+        assertEquals(index.recordsSnapshot(), reopened.recordsSnapshot());
+    }
+
     @Test
     public void conflictingActivationsAndFactsAfterSealAreRejectedWithoutDiskChanges() throws Exception {
         Path dimensionRoot = temporaryFolder.newFolder("sealed").toPath();