diff --git a/phpstan.neon b/phpstan.neon
index 5c4121c..b0a270c 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -3,6 +3,13 @@ includes:
 
 parameters:
     level: 10
+    # Analyse against the whole supported range, not whatever PHP happens to be
+    # running. Without this, syntax newer than the `Requires PHP: 8.1` header
+    # promises passes lint on a modern local PHP and only fails in the 8.1 test
+    # job — which is how a PHP 8.2 `true` return type once reached CI.
+    phpVersion:
+        min: 80100
+        max: 80300
     paths:
         - src
     bootstrapFiles:
diff --git a/src/Guardian/FamilyPage.php b/src/Guardian/FamilyPage.php
index a73468f..e93543f 100644
--- a/src/Guardian/FamilyPage.php
+++ b/src/Guardian/FamilyPage.php
@@ -144,18 +144,18 @@ class FamilyPage {
 		// phpcs:ignore WordPress.Security.NonceVerification.Missing -- nonce checked by the caller.
 		$childId = absint( Val::int( $_POST['child_id'] ?? 0 ) );
 
-		$result = $this->guardians->updateChild( $guardianId, $childId, $this->postString( 'child_name' ), $this->postString( 'child_dob' ) );
+		$error = $this->guardians->updateChild( $guardianId, $childId, $this->postString( 'child_name' ), $this->postString( 'child_dob' ) );
 
-		return $result instanceof \WP_Error ? $result : self::RESULT_UPDATED;
+		return $error ?? self::RESULT_UPDATED;
 	}
 
 	private function handleRemove( int $guardianId ): string|\WP_Error {
 		// phpcs:ignore WordPress.Security.NonceVerification.Missing -- nonce checked by the caller.
 		$childId = absint( Val::int( $_POST['child_id'] ?? 0 ) );
 
-		$result = $this->guardians->removeChild( $guardianId, $childId );
+		$error = $this->guardians->removeChild( $guardianId, $childId );
 
-		return $result instanceof \WP_Error ? $result : self::RESULT_REMOVED;
+		return $error ?? self::RESULT_REMOVED;
 	}
 
 	/**
diff --git a/src/Guardian/GuardianService.php b/src/Guardian/GuardianService.php
index 52a6cb7..315d7f0 100644
--- a/src/Guardian/GuardianService.php
+++ b/src/Guardian/GuardianService.php
@@ -99,8 +99,10 @@ class GuardianService {
 	 * Rename a child and update their date of birth. Refuses a student the caller
 	 * is not the guardian of, so the family screen cannot be turned into an
 	 * arbitrary user editor by posting someone else's id.
+	 *
+	 * Returns null on success, mirroring {@see \Unsupervised\Schedular\Registration\RegistrationGate::validate()}.
 	 */
-	public function updateChild( int $guardianId, int $studentId, string $name, string $dateOfBirth = '' ): true|\WP_Error {
+	public function updateChild( int $guardianId, int $studentId, string $name, string $dateOfBirth = '' ): ?\WP_Error {
 		if ( ! $this->guardians->isGuardianOf( $guardianId, $studentId ) ) {
 			return new \WP_Error( 'forbidden', __( 'That is not one of your children.', 'unsupervised-schedular' ) );
 		}
@@ -124,7 +126,7 @@ class GuardianService {
 
 		$this->setDateOfBirth( $studentId, $dateOfBirth );
 
-		return true;
+		return null;
 	}
 
 	/**
@@ -132,8 +134,10 @@ class GuardianService {
 	 * lesson or enrolment history: their id is referenced by lessons, payments and
 	 * credits, and deleting the user would orphan all of it. A studio admin
 	 * handles those cases by hand.
+	 *
+	 * Returns null on success.
 	 */
-	public function removeChild( int $guardianId, int $studentId ): true|\WP_Error {
+	public function removeChild( int $guardianId, int $studentId ): ?\WP_Error {
 		if ( ! $this->guardians->isGuardianOf( $guardianId, $studentId ) ) {
 			return new \WP_Error( 'forbidden', __( 'That is not one of your children.', 'unsupervised-schedular' ) );
 		}
@@ -148,7 +152,7 @@ class GuardianService {
 		$this->guardians->delete( $guardianId, $studentId );
 		$this->deleteUser( $studentId );
 
-		return true;
+		return null;
 	}
 
 	/**
diff --git a/tests/Unit/Guardian/FamilyPageTest.php b/tests/Unit/Guardian/FamilyPageTest.php
index 4a35d66..b7f183b 100644
--- a/tests/Unit/Guardian/FamilyPageTest.php
+++ b/tests/Unit/Guardian/FamilyPageTest.php
@@ -182,7 +182,7 @@ class FamilyPageTest extends TestCase
             'child_dob'        => '2015-04-02',
         ];
 
-        $this->guardians->shouldReceive('updateChild')->once()->with(5, 42, 'Ada L', '2015-04-02')->andReturn(true);
+        $this->guardians->shouldReceive('updateChild')->once()->with(5, 42, 'Ada L', '2015-04-02')->andReturn(null);
 
         $captured = null;
         $this->capturingPage($captured)->maybeHandleSubmit();
@@ -194,7 +194,7 @@ class FamilyPageTest extends TestCase
     {
         $_POST = ['us_family_action' => 'remove', 'child_id' => '42'];
 
-        $this->guardians->shouldReceive('removeChild')->once()->with(5, 42)->andReturn(true);
+        $this->guardians->shouldReceive('removeChild')->once()->with(5, 42)->andReturn(null);
 
         $captured = null;
         $this->capturingPage($captured)->maybeHandleSubmit();
diff --git a/tests/Unit/Guardian/GuardianServiceTest.php b/tests/Unit/Guardian/GuardianServiceTest.php
index 07b2beb..805aaae 100644
--- a/tests/Unit/Guardian/GuardianServiceTest.php
+++ b/tests/Unit/Guardian/GuardianServiceTest.php
@@ -236,7 +236,7 @@ class GuardianServiceTest extends TestCase
             ->with(['ID' => 42, 'display_name' => 'Ada L', 'nickname' => 'Ada L'])
             ->andReturn(42);
 
-        self::assertTrue($this->service->updateChild(5, 42, 'Ada L', '2015-04-02'));
+        self::assertNull($this->service->updateChild(5, 42, 'Ada L', '2015-04-02'));
         self::assertSame('2015-04-02', $this->meta[42][GuardianService::META_DOB]);
     }
 
@@ -249,7 +249,7 @@ class GuardianServiceTest extends TestCase
 
         Functions\expect('wp_delete_user')->once()->with(42);
 
-        self::assertTrue($this->service->removeChild(5, 42));
+        self::assertNull($this->service->removeChild(5, 42));
     }
 
     /**