diff --git a/src/main/java/org/springframework/samples/petclinic/owner/OwnerController.java b/src/main/java/org/springframework/samples/petclinic/owner/OwnerController.java
index 1ec50ee..498d494 100644
--- a/src/main/java/org/springframework/samples/petclinic/owner/OwnerController.java
+++ b/src/main/java/org/springframework/samples/petclinic/owner/OwnerController.java
@@ -140,9 +140,12 @@ private Page<Owner> findPaginatedForOwnersLastName(int page, String lastname) {
 		ControllerValidation.ValidatePageNumber(page);
 
 		int pageSize = 5;
-		Pageable pageable = PageRequest.of(page - 1, pageSize);
-		return owners.findByLastName(lastname, pageable);
+		int startPage = page - 1;
+
+		ControllerValidation.ValidatePageNumber(startPage);
+		Pageable pageable = PageRequest.of(startPage, pageSize);
 
+		return owners.findByLastName(lastname, pageable);
 	}
 
 	@GetMapping("/owners/{ownerId}/edit")
diff --git a/src/main/java/org/springframework/samples/petclinic/owner/PetController.java b/src/main/java/org/springframework/samples/petclinic/owner/PetController.java
index 4964f2b..78339e9 100644
--- a/src/main/java/org/springframework/samples/petclinic/owner/PetController.java
+++ b/src/main/java/org/springframework/samples/petclinic/owner/PetController.java
@@ -75,9 +75,7 @@ public Pet findPet(@PathVariable("ownerId") int ownerId,
 		}
 
 		Owner owner = this.owners.findById(ownerId);
-		if (owner == null) {
-			throw new IllegalArgumentException("Owner ID not found: " + ownerId);
-		}
+		ControllerValidation.ValidateNotNull(owner, "Owner");
 		return owner.getPet(petId);
 	}