diff --git a/src/main/java/org/springframework/samples/petclinic/mapper/PetMapper.java b/src/main/java/org/springframework/samples/petclinic/mapper/PetMapper.java
index c34ca224d..1a20bf4ac 100755
--- a/src/main/java/org/springframework/samples/petclinic/mapper/PetMapper.java
+++ b/src/main/java/org/springframework/samples/petclinic/mapper/PetMapper.java
@@ -1,6 +1,7 @@
 package org.springframework.samples.petclinic.mapper;
 
 import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
 import org.springframework.samples.petclinic.rest.dto.PetDto;
 import org.springframework.samples.petclinic.rest.dto.PetFieldsDto;
 import org.springframework.samples.petclinic.rest.dto.PetTypeDto;
@@ -14,6 +15,8 @@
  */
 @Mapper
 public interface PetMapper {
+
+    @Mapping(source = "owner.id", target = "ownerId")
     PetDto toPetDto(Pet pet);
 
     Collection<PetDto> toPetsDto(Collection<Pet> pets);
diff --git a/src/main/resources/openapi.yml b/src/main/resources/openapi.yml
index 188415ec0..93d56b01a 100755
--- a/src/main/resources/openapi.yml
+++ b/src/main/resources/openapi.yml
@@ -722,6 +722,14 @@ components:
               minimum: 0
               example: 1
               readOnly: true
+            ownerId:
+              title: Owner ID
+              description: The ID of the pet's owner.
+              type: integer
+              format: int32
+              minimum: 0
+              example: 1
+              readOnly: true
             visits:
               title: Visits
               description: Vet visit bookings for this pet.