diff --git a/src/FFMpeg/Format/ProgressListener/AbstractProgressListener.php b/src/FFMpeg/Format/ProgressListener/AbstractProgressListener.php
index f92dde1..3311266 100644
--- a/src/FFMpeg/Format/ProgressListener/AbstractProgressListener.php
+++ b/src/FFMpeg/Format/ProgressListener/AbstractProgressListener.php
@@ -179,6 +179,12 @@ abstract class AbstractProgressListener extends EventEmitter implements Listener
 
         if ($this->lastOutput !== null) {
             $delta = $currentTime - $this->lastOutput;
+
+            // Check the type of the currentSize variable and convert it to an integer if needed.
+            if(!is_numeric($currentSize)) {
+                $currentSize = (int)$currentSize;
+            }
+
             $deltaSize = $currentSize - $this->currentSize;
             $rate = $deltaSize * $delta;
             if ($rate > 0) {