diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e4c29d1..4103c86 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
         runs-on: ubuntu-latest
         strategy:
             matrix:
-                php: 
+                php:
                   - '7.4'
                   - '8.0'
                   - '8.1'
@@ -26,4 +26,5 @@ jobs:
             -   run: composer install --no-progress
 #            -   run: composer codestyle
             -   run: composer phpstan
+                if:  matrix.php == '8.1'
             -   run: composer tests
diff --git a/Michelf/MarkdownExtra.php b/Michelf/MarkdownExtra.php
index 060a4ae..796949e 100644
--- a/Michelf/MarkdownExtra.php
+++ b/Michelf/MarkdownExtra.php
@@ -601,6 +601,7 @@ class MarkdownExtra extends \Michelf\Markdown {
 			else {
 				$parsed .= $tag;
 			}
+			// @phpstan-ignore-next-line
 		} while ($depth >= 0);
 
 		return array($parsed, $text);
diff --git a/composer.json b/composer.json
index 07f5a5b..7cb59cf 100644
--- a/composer.json
+++ b/composer.json
@@ -24,11 +24,10 @@
  		"psr-4": { "Michelf\\": "Michelf/" }
 	},
 	"require-dev": {
-		"phpspec/prophecy": "^1.6",
 		"friendsofphp/php-cs-fixer": "^3.0",
 		"phpunit/phpunit": "^9.5",
-		"phpstan/phpstan": "^1.0",
-		"phpstan/phpstan-phpunit": "^1.0"
+		"phpstan/phpstan": ">=1.0",
+		"phpstan/phpstan-phpunit": ">=1.0"
 	},
 
 	"scripts": {
diff --git a/test/helpers/MarkdownTestHelper.php b/test/helpers/MarkdownTestHelper.php
index ffca0c9..fc74636 100644
--- a/test/helpers/MarkdownTestHelper.php
+++ b/test/helpers/MarkdownTestHelper.php
@@ -22,7 +22,6 @@ class MarkdownTestHelper
 
 		$dataValues = array();
 
-		/** @var SplFileInfo $inputFile */
 		foreach ($regexIterator as $inputFiles) {
 			foreach ($inputFiles as $inputMarkdownPath) {
 				$xhtml = true;
@@ -163,6 +162,7 @@ class MarkdownTestHelper
 		foreach ($node_list as $node) {
 			switch ($node->nodeType) {
 				case XML_ELEMENT_NODE:
+					/** @var DOMElement $node */
 					static::normalizeElementContent($node, $whitespace_preserve);
 					static::normalizeElementAttributes($node);
 
@@ -207,6 +207,7 @@ class MarkdownTestHelper
 					break;
 
 				case XML_TEXT_NODE:
+					/** @var DOMText $node */
 					if (!$whitespace_preserve) {
 						if (trim($node->data) === "") {
 							$node->data = $whitespace;
@@ -222,8 +223,8 @@ class MarkdownTestHelper
 			($whitespace === "\n\n" || $whitespace === "\n")) {
 			if ($element->firstChild) {
 				if ($element->firstChild->nodeType == XML_TEXT_NODE) {
-					$element->firstChild->data =
-						preg_replace('{^\s+}', "\n", $element->firstChild->data);
+					$element->firstChild->data = // @phpstan-ignore-line
+						preg_replace('{^\s+}', "\n", $element->firstChild->data ?? '');
 				}
 				else {
 					$element->insertBefore(new DOMText("\n"), $element->firstChild);
@@ -231,8 +232,8 @@ class MarkdownTestHelper
 			}
 			if ($element->lastChild) {
 				if ($element->lastChild->nodeType == XML_TEXT_NODE) {
-					$element->lastChild->data =
-						preg_replace('{\s+$}', "\n", $element->lastChild->data);
+					$element->lastChild->data = // @phpstan-ignore-line
+						preg_replace('{\s+$}', "\n", $element->lastChild->data ?? '');
 				}
 				else {
 					$element->insertBefore(new DOMText("\n"), null);