diff --git a/src/wp-includes/class-wp-duotone.php b/src/wp-includes/class-wp-duotone.php
index 194b649843..40e9f7548b 100644
--- a/src/wp-includes/class-wp-duotone.php
+++ b/src/wp-includes/class-wp-duotone.php
@@ -209,10 +209,7 @@ class WP_Duotone {
 			'rad'  => 360 / ( M_PI * 2 ),
 		);
 
-		$factor = $angle_units[ $unit ];
-		if ( ! $factor ) {
-			$factor = 1;
-		}
+		$factor = isset( $angle_units[ $unit ] ) ? $angle_units[ $unit ] : 1;
 
 		return (float) $value * $factor;
 	}
diff --git a/tests/phpunit/tests/block-supports/duotone.php b/tests/phpunit/tests/block-supports/duotone.php
index faeeaa2b40..5a31dc9362 100644
--- a/tests/phpunit/tests/block-supports/duotone.php
+++ b/tests/phpunit/tests/block-supports/duotone.php
@@ -5,7 +5,7 @@
  *
  * @group block-supports
  *
- * @package WordPress
+ * @coversDefaultClass WP_Duotone
  */
 
 class Tests_Block_Supports_Duotone extends WP_UnitTestCase {
@@ -166,4 +166,32 @@ class Tests_Block_Supports_Duotone extends WP_UnitTestCase {
 			'invalid'                         => array( 'not a valid attribute', false ),
 		);
 	}
+
+	/**
+	 * @dataProvider data_colord_parse_hue
+	 * @ticket 59496
+	 */
+	public function test_colord_parse_hue( $value, $unit, $expected ) {
+		$reflection = new ReflectionMethod( 'WP_Duotone', 'colord_parse_hue' );
+		$reflection->setAccessible( true );
+
+		$this->assertSame( $expected, $reflection->invoke( null, $value, $unit ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[].
+	 */
+	public function data_colord_parse_hue() {
+		return array(
+			'deg-angle-unit'                => array( 120, 'deg', 120.0 ),
+			'grad-angle-unit'               => array( 120, 'grad', 108.0 ),
+			'turn-angle-unit'               => array( 120, 'turn', 43200.0 ),
+			'rad-angle-unit'                => array( 120, 'rad', 6875.493541569878 ),
+			'empty-angle-unit'              => array( 120, '', 120.0 ),
+			'invalid-angle-unit'            => array( 120, 'invalid', 120.0 ),
+			'negative-value-deg-angle-unit' => array( -120, 'deg', -120.0 ),
+		);
+	}
 }