diff --git a/src/ColorModels/AbstractColorModel.php b/src/ColorModels/AbstractColorModel.php
index 5db61f3..4e85a57 100644
--- a/src/ColorModels/AbstractColorModel.php
+++ b/src/ColorModels/AbstractColorModel.php
@@ -8,7 +8,7 @@ use InvalidArgumentException;
 abstract class AbstractColorModel
 {
 
-    protected function checkValue(float $value)
+    protected function checkValue(float $value): void
     {
         if ($value > 1.0) {
             throw new InvalidArgumentException('Ein Wert größer als 1 ist nicht definierbar.');
diff --git a/src/Transformer/Utilities/AbstractHueSaturationValueToUtility.php b/src/Transformer/Utilities/AbstractHueSaturationValueToUtility.php
index d237a04..d578fe5 100644
--- a/src/Transformer/Utilities/AbstractHueSaturationValueToUtility.php
+++ b/src/Transformer/Utilities/AbstractHueSaturationValueToUtility.php
@@ -44,6 +44,11 @@ abstract class AbstractHueSaturationValueToUtility
 
     abstract protected function splitColor(): void;
 
+    /**
+     * @param bool $reciprocal
+     *
+     * @return float
+     */
     protected function calcColorValue($reciprocal = false): float
     {
         // Rest-Anteil am Vollkreis des aktuellen Intervals als Wert '[0,1]'