diff --git a/hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java b/hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java
index 488239b5cba6..7e81335112f6 100644
--- a/hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java
+++ b/hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java
@@ -1605,7 +1605,9 @@ private Object initLazyProperties(
 
 		final var interceptor = asPersistentAttributeInterceptable( entity ).$$_hibernate_getInterceptor();
 		assert interceptor != null : "Expecting bytecode interceptor to be non-null";
-		final Set<String> initializedLazyAttributeNames = interceptor.getInitializedLazyAttributeNames();
+		// Create a copy of init attrs, since lazySelectLoadPlan.load may update the set inside the interceptor,
+		// and we end up with the modified one here:
+		final Set<String> initializedLazyAttributeNames = new HashSet<>( interceptor.getInitializedLazyAttributeNames() );
 
 		final var lazyAttributesMetadata = getBytecodeEnhancementMetadata().getLazyAttributesMetadata();
 		final String fetchGroup = lazyAttributesMetadata.getFetchGroupName( fieldName );
diff --git a/hibernate-core/src/test/java/org/hibernate/orm/test/mapping/lazytoone/LazyOneToOneWithCastTest.java b/hibernate-core/src/test/java/org/hibernate/orm/test/mapping/lazytoone/LazyOneToOneWithCastTest.java
new file mode 100644
index 000000000000..c759b2178b53
--- /dev/null
+++ b/hibernate-core/src/test/java/org/hibernate/orm/test/mapping/lazytoone/LazyOneToOneWithCastTest.java
@@ -0,0 +1,191 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.mapping.lazytoone;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.Id;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.OneToOne;
+import org.hibernate.Hibernate;
+import org.hibernate.annotations.LazyGroup;
+import org.hibernate.testing.bytecode.enhancement.EnhancementOptions;
+import org.hibernate.testing.bytecode.enhancement.extension.BytecodeEnhanced;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DomainModel(
+		annotatedClasses = {
+				LazyOneToOneWithCastTest.ContainingEntity.class,
+				LazyOneToOneWithCastTest.ContainedEntity.class,
+		}
+)
+@SessionFactory
+@BytecodeEnhanced
+@EnhancementOptions(lazyLoading = true)
+class LazyOneToOneWithCastTest {
+
+	@Test
+	void oneNullOneNotNull(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			ContainingEntity containingEntity1 = new ContainingEntity();
+			containingEntity1.setId( 2 );
+
+			ContainedEntity contained1 = new ContainedEntity();
+			contained1.setId( 4 );
+			contained1.setContainingAsIndexedEmbeddedWithCast( containingEntity1 );
+			containingEntity1.setContainedIndexedEmbeddedWithCast( contained1 );
+
+			session.persist( contained1 );
+			session.persist( containingEntity1 );
+
+		} );
+
+		scope.inTransaction( session -> {
+			ContainedEntity contained = session.find( ContainedEntity.class, 4 );
+
+			ContainingEntity containingAsIndexedEmbedded = contained.getContainingAsIndexedEmbedded();
+			assertThat( containingAsIndexedEmbedded ).isNull();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbedded" ) ).isTrue();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbeddedWithCast" ) ).isFalse();
+
+			Object containingAsIndexedEmbeddedWithCast = contained.getContainingAsIndexedEmbeddedWithCast();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbeddedWithCast" ) ).isTrue();
+			assertThat( containingAsIndexedEmbeddedWithCast ).isNotNull();
+		} );
+
+		scope.inTransaction( session -> {
+			ContainedEntity contained = session.find( ContainedEntity.class, 4 );
+			assertThat( contained.getContainingAsIndexedEmbeddedWithCast() ).isNotNull();
+		} );
+	}
+
+	@Test
+	void bothNotNull(SessionFactoryScope scope) {
+		scope.inTransaction( session -> {
+			ContainingEntity containingEntity1 = new ContainingEntity();
+			containingEntity1.setId( 1 );
+
+			ContainedEntity contained1 = new ContainedEntity();
+			contained1.setId( 4 );
+			contained1.setContainingAsIndexedEmbeddedWithCast( containingEntity1 );
+			containingEntity1.setContainedIndexedEmbeddedWithCast( contained1 );
+
+			contained1.setContainingAsIndexedEmbedded( containingEntity1 );
+			containingEntity1.setContainedIndexedEmbedded( contained1 );
+
+
+			session.persist( contained1 );
+			session.persist( containingEntity1 );
+
+		} );
+
+		scope.inTransaction( session -> {
+			ContainedEntity contained = session.find( ContainedEntity.class, 4 );
+
+			ContainingEntity containingAsIndexedEmbedded = contained.getContainingAsIndexedEmbedded();
+			assertThat( containingAsIndexedEmbedded ).isNotNull();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbedded" ) ).isTrue();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbeddedWithCast" ) ).isFalse();
+
+			Object containingAsIndexedEmbeddedWithCast = contained.getContainingAsIndexedEmbeddedWithCast();
+			assertThat( Hibernate.isPropertyInitialized( contained, "containingAsIndexedEmbeddedWithCast" ) ).isTrue();
+			assertThat( containingAsIndexedEmbeddedWithCast ).isNotNull();
+		} );
+
+		scope.inTransaction( session -> {
+			ContainedEntity contained = session.find( ContainedEntity.class, 4 );
+			assertThat( contained.getContainingAsIndexedEmbeddedWithCast() ).isNotNull();
+		} );
+	}
+
+	@AfterEach
+	void tearDown(SessionFactoryScope scope) {
+		scope.getSessionFactory().getSchemaManager().truncateMappedObjects();
+	}
+
+	@Entity(name = "containing")
+	public static class ContainingEntity {
+
+		@Id
+		private Integer id;
+
+		@OneToOne
+		private ContainedEntity containedIndexedEmbedded;
+
+		@OneToOne(targetEntity = ContainedEntity.class)
+		@JoinColumn(name = "CIndexedEmbeddedCast")
+		private ContainedEntity containedIndexedEmbeddedWithCast;
+
+
+		public Integer getId() {
+			return id;
+		}
+
+		public void setId(Integer id) {
+			this.id = id;
+		}
+
+		public ContainedEntity getContainedIndexedEmbedded() {
+			return containedIndexedEmbedded;
+		}
+
+		public Object getContainedIndexedEmbeddedWithCast() {
+			return containedIndexedEmbeddedWithCast;
+		}
+
+		public void setContainedIndexedEmbeddedWithCast(ContainedEntity containedIndexedEmbeddedWithCast) {
+			this.containedIndexedEmbeddedWithCast = containedIndexedEmbeddedWithCast;
+		}
+
+		public void setContainedIndexedEmbedded(ContainedEntity containedIndexedEmbedded) {
+			this.containedIndexedEmbedded = containedIndexedEmbedded;
+		}
+	}
+
+	@Entity(name = "contained")
+	public static class ContainedEntity {
+		@Id
+		private Integer id;
+
+		@OneToOne(mappedBy = "containedIndexedEmbeddedWithCast", targetEntity = ContainingEntity.class,
+				fetch = FetchType.LAZY)
+		@LazyGroup("containingAsIndexedEmbeddedWithCast")
+		private ContainingEntity containingAsIndexedEmbeddedWithCast;
+
+		@OneToOne(mappedBy = "containedIndexedEmbedded", fetch = FetchType.LAZY)
+		@LazyGroup("containingAsIndexedEmbedded")
+		private ContainingEntity containingAsIndexedEmbedded;
+
+		public Integer getId() {
+			return id;
+		}
+
+		public void setId(Integer id) {
+			this.id = id;
+		}
+
+		public ContainingEntity getContainingAsIndexedEmbedded() {
+			return containingAsIndexedEmbedded;
+		}
+
+		public Object getContainingAsIndexedEmbeddedWithCast() {
+			return containingAsIndexedEmbeddedWithCast;
+		}
+
+		public void setContainingAsIndexedEmbeddedWithCast(ContainingEntity containingAsIndexedEmbeddedWithCast) {
+			this.containingAsIndexedEmbeddedWithCast = containingAsIndexedEmbeddedWithCast;
+		}
+
+		public void setContainingAsIndexedEmbedded(ContainingEntity containingAsIndexedEmbedded) {
+			this.containingAsIndexedEmbedded = containingAsIndexedEmbedded;
+		}
+	}
+}