diff --git a/typo3/sysext/core/Classes/Imaging/GraphicalFunctions.php b/typo3/sysext/core/Classes/Imaging/GraphicalFunctions.php
index b2055a741220..ad9487d88d59 100644
--- a/typo3/sysext/core/Classes/Imaging/GraphicalFunctions.php
+++ b/typo3/sysext/core/Classes/Imaging/GraphicalFunctions.php
@@ -740,6 +740,10 @@ public function calcBBox($conf)
         }
         // Set original lineHeight (used by line breaks):
         $theBBoxInfo['lineHeight'] = $y;
+        if (!empty($conf['lineHeight'])) {
+            $theBBoxInfo['lineHeight'] = (int)$conf['lineHeight'];
+        }
+
         // If any kind of spacing applys, we use this function:
         if ($spacing || $wordSpacing) {
             $x = 0;