diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 969d7b8..46a5ceb 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -15,6 +15,11 @@ jobs:
         name: P${{ matrix.php }} - ${{ matrix.dependency-version }} - ${{ matrix.os }}
 
         steps:
+            -   name: Upgrade ghostscript
+                run: |
+                    sudo apt-get update
+                    sudo apt-get install ghostscript
+
             - name: Checkout code
               uses: actions/checkout@v3
 
diff --git a/composer.json b/composer.json
index d52489a..9bc04df 100644
--- a/composer.json
+++ b/composer.json
@@ -37,5 +37,11 @@
     },
     "scripts": {
         "test": "vendor/bin/pest"
+    },
+    "config": {
+        "sort-packages": true,
+        "allow-plugins": {
+            "pestphp/pest-plugin": true
+        }
     }
 }
diff --git a/src/Pdf.php b/src/Pdf.php
index b990eb3..2bf06d0 100644
--- a/src/Pdf.php
+++ b/src/Pdf.php
@@ -42,9 +42,7 @@ public function __construct(string $pdfFile)
 
         $this->imagick = new Imagick();
 
-        $this->imagick->pingImage($pdfFile);
-
-        $this->numberOfPages = $this->imagick->getNumberImages();
+        $this->imagick->readImage($this->pdfFile);
     }
 
     public function setResolution(int $resolution)
@@ -109,6 +107,10 @@ public function setPage(int $page)
 
     public function getNumberOfPages(): int
     {
+        if ($this->numberOfPages === null) {
+            $this->numberOfPages = $this->imagick->getNumberImages();
+        }
+
         return $this->numberOfPages;
     }