diff --git a/src/wp-includes/class-wp-icons-registry.php b/src/wp-includes/class-wp-icons-registry.php
index b096610c1b04f..2e2c2ca2956b4 100644
--- a/src/wp-includes/class-wp-icons-registry.php
+++ b/src/wp-includes/class-wp-icons-registry.php
@@ -81,8 +81,8 @@ protected function __construct() {
 			$this->register(
 				'core/' . $icon_name,
 				array(
-					'label'    => $icon_data['label'],
-					'filePath' => $icons_directory . $icon_data['filePath'],
+					'label'     => $icon_data['label'],
+					'file_path' => $icons_directory . $icon_data['filePath'],
 				)
 			);
 		}
@@ -97,11 +97,11 @@ protected function __construct() {
 	 * @param array  $icon_properties {
 	 *     List of properties for the icon.
 	 *
-	 *     @type string $label    Required. A human-readable label for the icon.
-	 *     @type string $content  Optional. SVG markup for the icon.
-	 *                            If not provided, the content will be retrieved from the `filePath` if set.
-	 *                            If both `content` and `filePath` are not set, the icon will not be registered.
-	 *     @type string $filePath Optional. The full path to the file containing the icon content.
+	 *     @type string $label     Required. A human-readable label for the icon.
+	 *     @type string $content   Optional. SVG markup for the icon.
+	 *                             If not provided, the content will be retrieved from the `file_path` if set.
+	 *                             If both `content` and `file_path` are not set, the icon will not be registered.
+	 *     @type string $file_path Optional. The full path to the file containing the icon content.
 	 * }
 	 * @return bool True if the icon was registered with success and false otherwise.
 	 */
@@ -143,7 +143,7 @@ protected function register( $icon_name, $icon_properties ) {
 			return false;
 		}
 
-		$allowed_keys = array_fill_keys( array( 'label', 'content', 'filePath' ), 1 );
+		$allowed_keys = array_fill_keys( array( 'label', 'content', 'file_path' ), 1 );
 		foreach ( array_keys( $icon_properties ) as $key ) {
 			if ( ! array_key_exists( $key, $allowed_keys ) ) {
 				_doing_it_wrong(
@@ -169,12 +169,12 @@ protected function register( $icon_name, $icon_properties ) {
 		}
 
 		if (
-			( ! isset( $icon_properties['content'] ) && ! isset( $icon_properties['filePath'] ) ) ||
-			( isset( $icon_properties['content'] ) && isset( $icon_properties['filePath'] ) )
+			( ! isset( $icon_properties['content'] ) && ! isset( $icon_properties['file_path'] ) ) ||
+			( isset( $icon_properties['content'] ) && isset( $icon_properties['file_path'] ) )
 		) {
 			_doing_it_wrong(
 				__METHOD__,
-				__( 'Icons must provide either `content` or `filePath`.' ),
+				__( 'Icons must provide either `content` or `file_path`.' ),
 				'7.0.0'
 			);
 			return false;
@@ -262,7 +262,7 @@ protected function sanitize_icon_content( $icon_content ) {
 	protected function get_content( $icon_name ) {
 		if ( ! isset( $this->registered_icons[ $icon_name ]['content'] ) ) {
 			$content = file_get_contents(
-				$this->registered_icons[ $icon_name ]['filePath']
+				$this->registered_icons[ $icon_name ]['file_path']
 			);
 			$content = $this->sanitize_icon_content( $content );
 
diff --git a/tests/phpunit/tests/icons/wpIconsRegistry.php b/tests/phpunit/tests/icons/wpIconsRegistry.php
index fba2eacde43f5..23352964db0f5 100644
--- a/tests/phpunit/tests/icons/wpIconsRegistry.php
+++ b/tests/phpunit/tests/icons/wpIconsRegistry.php
@@ -40,7 +40,7 @@ public function tear_down() {
 	 * Invokes WP_Icons_Registry::register despite it being private
 	 *
 	 * @param string $icon_name       Icon name including namespace.
-	 * @param array  $icon_properties Icon properties (label, content, filePath).
+	 * @param array  $icon_properties Icon properties (label, content, file_path).
 	 * @return bool True if the icon was registered successfully.
 	 */
 	private function register( $icon_name, $icon_properties ) {
@@ -107,4 +107,74 @@ public function test_register_invalid_name( $icon_name ) {
 		$result = $this->register( $icon_name, $settings );
 		$this->assertFalse( $result );
 	}
+
+	/**
+	 * Should register an icon that provides its content through `file_path`.
+	 *
+	 * @ticket 64847
+	 *
+	 * @covers ::register
+	 */
+	public function test_register_icon_with_file_path() {
+		$file_path = tempnam( get_temp_dir(), 'wp-icon-' );
+		file_put_contents( $file_path, '<svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"></svg>' );
+
+		$name     = 'test-plugin/file-path-icon';
+		$settings = array(
+			'label'     => 'Icon',
+			'file_path' => $file_path,
+		);
+
+		$result = $this->register( $name, $settings );
+		$this->assertTrue( $result );
+		$this->assertTrue( $this->registry->is_registered( $name ) );
+
+		$registered_icons = $this->registry->get_registered_icons( $name );
+		$this->assertCount( 1, $registered_icons );
+		$this->assertStringContainsString( '<svg', $registered_icons[0]['content'] );
+
+		unlink( $file_path );
+	}
+
+	/**
+	 * Should fail to register an icon that provides both `content` and `file_path`.
+	 *
+	 * @ticket 64847
+	 *
+	 * @covers ::register
+	 *
+	 * @expectedIncorrectUsage WP_Icons_Registry::register
+	 */
+	public function test_register_icon_with_content_and_file_path() {
+		$name     = 'test-plugin/content-and-file-path';
+		$settings = array(
+			'label'     => 'Icon',
+			'content'   => '<svg></svg>',
+			'file_path' => '/path/to/icon.svg',
+		);
+
+		$result = $this->register( $name, $settings );
+		$this->assertFalse( $result );
+		$this->assertFalse( $this->registry->is_registered( $name ) );
+	}
+
+	/**
+	 * Should fail to register an icon that provides neither `content` nor `file_path`.
+	 *
+	 * @ticket 64847
+	 *
+	 * @covers ::register
+	 *
+	 * @expectedIncorrectUsage WP_Icons_Registry::register
+	 */
+	public function test_register_icon_without_content_or_file_path() {
+		$name     = 'test-plugin/no-content';
+		$settings = array(
+			'label' => 'Icon',
+		);
+
+		$result = $this->register( $name, $settings );
+		$this->assertFalse( $result );
+		$this->assertFalse( $this->registry->is_registered( $name ) );
+	}
 }