diff --git a/composer.json b/composer.json
index 4b95b66..b69847d 100644
--- a/composer.json
+++ b/composer.json
@@ -32,9 +32,9 @@
         "erusev/parsedown": "^1.7",
         "erusev/parsedown-extra": "^0.8",
         "phpstan/phpstan": "^0.12",
-        "phpstan/phpstan-strict-rules": "^0.12.0",
-        "phpstan/phpstan-webmozart-assert": "^0.12.0",
-        "phpstan/phpstan-phpunit": "^0.12.0",
+        "phpstan/phpstan-strict-rules": "^0.12",
+        "phpstan/phpstan-webmozart-assert": "^0.12",
+        "phpstan/phpstan-phpunit": "^0.12",
         "phpunit/phpunit": "^8.4",
         "pixelrobin/php-feather": "^1.0",
         "symfony/filesystem": "^4.2 || ^5.0",
diff --git a/phpstan.neon b/phpstan.neon
index e94d760..2d17bd4 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -18,6 +18,14 @@ parameters:
         -
             message: "#no value type specified in iterable type Symfony\\\\Component\\\\Process\\\\Process#"
             path: %currentWorkingDirectory%
+
+        # It's checked by Assert:count(1)
+        -
+            message: "#^Parameter \\#1 \\$language of function Safe\\\\pspell_config_create expects string, string\\|false given\\.$#"
+            count: 1
+            path: src/Spellchecker/PHPPspell.php
+
+
         # Missing strict comparison
         - '#^Construct empty\(\) is not allowed. Use more strict comparison.$#'
 #        - '#^Only booleans are allowed in#'
diff --git a/renovate.json b/renovate.json
index 878720c..5fcce11 100644
--- a/renovate.json
+++ b/renovate.json
@@ -1,6 +1,6 @@
 {
-    "extends": [
-        "config:base"
-    ],
-    "rangeStrategy": "replace"
+  "extends": [
+    "config:base",
+    ":preserveSemverRanges"
+  ]
 }
diff --git a/src/Source/Directory.php b/src/Source/Directory.php
index 03c8ccd..2206e65 100644
--- a/src/Source/Directory.php
+++ b/src/Source/Directory.php
@@ -4,6 +4,7 @@
 
 namespace PhpSpellcheck\Source;
 
+use PhpSpellcheck\Exception\RuntimeException;
 use PhpSpellcheck\Text;
 
 class Directory implements SourceInterface
@@ -57,9 +58,11 @@ private function getContents(): iterable
         foreach ($filesInDir as $file) {
             if (\is_string($file)) {
                 $file = new \SplFileInfo($file);
-            } elseif (\is_array($file)) {
+            } elseif (\is_array($file) && !empty($file)) {
                 // When regex pattern is used, an array containing the file path in its first element is returned
                 $file = new \SplFileInfo(current($file));
+            } else {
+                throw new RuntimeException(\Safe\sprintf('Couldn\'t create "%s" object from the given file', \SplFileInfo::class));
             }
 
             if (!$file->isDir() && $file->getRealPath() !== false) {
diff --git a/src/Spellchecker/PHPPspell.php b/src/Spellchecker/PHPPspell.php
index 84a49cc..53d438f 100644
--- a/src/Spellchecker/PHPPspell.php
+++ b/src/Spellchecker/PHPPspell.php
@@ -51,7 +51,7 @@ public function check(
         array $languages,
         array $context
     ): iterable {
-        Assert::count($languages, 1, 'PHPPspell spellchecker doesn\'t support multiple languages check');
+        Assert::count($languages, 1, 'PHPPspell spellchecker doesn\'t support multi-language check');
 
         $pspellConfig = \Safe\pspell_config_create(current($languages));
         \Safe\pspell_config_mode($pspellConfig, $this->mode);
@@ -66,6 +66,11 @@ public function check(
             foreach ($words as $key => $word) {
                 if (!pspell_check($dictionary, $word)) {
                     $suggestions = pspell_suggest($dictionary, $word);
+
+                    Assert::isArray(
+                        $suggestions,
+                        \Safe\sprintf('pspell_suggest method failed with dictionary "%s" and word "%s"', $dictionary, $word)
+                    );
                     yield new Misspelling($word, 0, $lineNumber + 1, $suggestions, $context);
                 }
             }
diff --git a/src/Utils/LineAndOffset.php b/src/Utils/LineAndOffset.php
index 1937407..872d404 100644
--- a/src/Utils/LineAndOffset.php
+++ b/src/Utils/LineAndOffset.php
@@ -21,7 +21,7 @@ class LineAndOffset
     public static function findFromFirstCharacterOffset(string $text, int $offsetFromFirstCharacter): array
     {
         // positive offset
-        Assert::greaterThanEq($offsetFromFirstCharacter, 0, sprintf('Offset must be a positive integer, "%s" given', $offsetFromFirstCharacter));
+        Assert::greaterThanEq($offsetFromFirstCharacter, 0, \Safe\sprintf('Offset must be a positive integer, "%s" given', $offsetFromFirstCharacter));
 
         $textLength = mb_strlen($text);
         if ($textLength < $offsetFromFirstCharacter) {