diff --git a/src/KeyFactory.php b/src/KeyFactory.php
index 0bcf3c9..ab82ca8 100644
--- a/src/KeyFactory.php
+++ b/src/KeyFactory.php
@@ -611,7 +611,7 @@ public static function loadSignatureKeyPair(string $filePath): SignatureKeyPair
     /**
      * Export a cryptography key to a string (with a checksum)
      *
-     * @param $key
+     * @param Key|KeyPair $key
      * @return HiddenString
      * @throws \TypeError
      */
diff --git a/src/Stream/MutableFile.php b/src/Stream/MutableFile.php
index ba4c0b2..ce7d78a 100644
--- a/src/Stream/MutableFile.php
+++ b/src/Stream/MutableFile.php
@@ -44,13 +44,13 @@ class MutableFile implements StreamInterface
 
     /**
      * MutableFile constructor.
-     * @param $file
+     * @param string|resource $file
      * @throws CryptoException\InvalidType
      * @throws CryptoException\FileAccessDenied
      */
     public function __construct($file)
     {
-        if (is_string($file)) {
+        if (\is_string($file)) {
             $fp = \fopen($file, 'wb');
             if (!\is_resource($fp)) {
                 throw new CryptoException\FileAccessDenied(
@@ -61,7 +61,7 @@ public function __construct($file)
             $this->closeAfter = true;
             $this->pos = 0;
             $this->stat = \fstat($this->fp);
-        } elseif (is_resource($file)) {
+        } elseif (\is_resource($file)) {
             $this->fp = $file;
             $this->pos = \ftell($this->fp);
             $this->stat = \fstat($this->fp);
diff --git a/src/Stream/ReadOnlyFile.php b/src/Stream/ReadOnlyFile.php
index e2abb86..8ca6f70 100644
--- a/src/Stream/ReadOnlyFile.php
+++ b/src/Stream/ReadOnlyFile.php
@@ -54,7 +54,7 @@ class ReadOnlyFile implements StreamInterface
     /**
      * ReadOnlyFile constructor
      *
-     * @param $file
+     * @param string|resource $file
      * @param Key|null $key
      * @throws CryptoException\InvalidType
      * @throws CryptoException\FileAccessDenied