diff --git a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
index fdadb6518159b..0fd23231ca5f1 100644
--- a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
+++ b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
@@ -421,7 +421,15 @@ private function process_directives_args( string $html, array &$context_stack, a
 	 */
 	private function evaluate( $directive_value, string $default_namespace, $context = false ) {
 		list( $ns, $path ) = $this->extract_directive_value( $directive_value, $default_namespace );
-		if ( empty( $path ) ) {
+		if ( 'null' === $default_namespace ) {
+			$message = 'The namespace defined cannot be null.';
+			_doing_it_wrong( __METHOD__, $message, '6.6.0' );
+			return null;
+		}
+		if ( empty( $ns ) || empty( $path ) ) {
+			/* translators: %s: The directive value referenced. */
+			$message = sprintf( 'Namespace or reference path cannot be empty. Directive value referenced: %s ', $directive_value );
+			_doing_it_wrong( __METHOD__, $message, '6.6.0' );
 			return null;
 		}
 
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
index 8af2da1cd0861..86eeabc05fd75 100644
--- a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
@@ -814,7 +814,7 @@ public function test_process_directives_does_not_change_inner_html_in_math() {
 	 * @param string $directive_value The directive attribute value to evaluate.
 	 * @return mixed The result of the evaluate method.
 	 */
-	private function evaluate( $directive_value ) {
+	private function evaluate( $directive_value, $default_namespace = 'myPlugin' ) {
 		$generate_state = function ( $name ) {
 			return array(
 				'key'    => $name,
@@ -829,7 +829,7 @@ private function evaluate( $directive_value ) {
 		);
 		$evaluate = new ReflectionMethod( $this->interactivity, 'evaluate' );
 		$evaluate->setAccessible( true );
-		return $evaluate->invokeArgs( $this->interactivity, array( $directive_value, 'myPlugin', $context ) );
+		return $evaluate->invokeArgs( $this->interactivity, array( $directive_value, $default_namespace, $context ) );
 	}
 
 	/**
@@ -923,6 +923,25 @@ public function test_evaluate_nested_value() {
 		$this->assertEquals( 'otherPlugin-context-nested', $result );
 	}
 
+	/**
+	 * Tests the `evaluate` method for non valid namespace values.
+	 *
+	 * @ticket 61044
+	 *
+	 * @covers ::evaluate
+	 * @expectedIncorrectUsage WP_Interactivity_API::evaluate
+	 */
+	public function test_evaluate_unvalid_namespaces() {
+		$result = $this->evaluate( 'path', 'null' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'path', '' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'path', '{}' );
+		$this->assertNull( $result );
+	}
+
 	/**
 	 * Tests the `kebab_to_camel_case` method.
 	 *