diff --git a/src/Stream/OptimalTransferEncodedPhraseStream.php b/src/Stream/OptimalTransferEncodedPhraseStream.php
index 1ac38a3..655fac0 100644
--- a/src/Stream/OptimalTransferEncodedPhraseStream.php
+++ b/src/Stream/OptimalTransferEncodedPhraseStream.php
@@ -48,17 +48,19 @@ public function __construct(string $text, int $lineLength = 78, string $lineBrea
      */
     private function calculateOptimalStream(string $text): StreamInterface
     {
-        if (\strcspn($text, self::NON_7BIT_CHARS) === \strlen($text)) {
+        $length = \strlen($text);
+
+        if (\strcspn($text, self::NON_7BIT_CHARS) === $length) {
             $this->encoding = '7bit';
             return new AsciiEncodedStream($text, $this->lineLength, $this->lineBreak);
         }
 
-        if (\strcspn($text, HeaderValueParameter::RFC_822_T_SPECIAL) !== \strlen($text)) {
+        if (\strcspn($text, HeaderValueParameter::RFC_822_T_SPECIAL) !== $length) {
             $this->encoding = 'base64';
             return Base64EncodedStream::fromString($text, $this->lineLength, $this->lineBreak);
         }
 
-        if (\preg_match_all('/[\000-\010\013\014\016-\037\177-\377]/', $text) > (\strlen($text) / 3)) {
+        if (\preg_match_all('/[\000-\010\013\014\016-\037\177-\377]/', $text) > ($length / 3)) {
             $this->encoding = 'base64';
             return Base64EncodedStream::fromString($text, $this->lineLength, $this->lineBreak);
         }
diff --git a/src/Stream/OptimalTransferEncodedTextStream.php b/src/Stream/OptimalTransferEncodedTextStream.php
index 9c5a63e..1edb693 100644
--- a/src/Stream/OptimalTransferEncodedTextStream.php
+++ b/src/Stream/OptimalTransferEncodedTextStream.php
@@ -47,12 +47,14 @@ public function __construct(string $text, int $lineLength = 78, string $lineBrea
      */
     private function calculateOptimalStream(string $text): StreamInterface
     {
-        if (\strcspn($text, self::NON_7BIT_CHARS) === \strlen($text)) {
+        $length = \strlen($text);
+
+        if (\strcspn($text, self::NON_7BIT_CHARS) === $length) {
             $this->encoding = '7bit';
             return new AsciiEncodedStream($text, $this->lineLength, $this->lineBreak);
         }
 
-        if (\preg_match_all('/[\000-\010\013\014\016-\037\177-\377]/', $text) > (\strlen($text) / 3)) {
+        if (\preg_match_all('/[\000-\010\013\014\016-\037\177-\377]/', $text) > ($length / 3)) {
             $this->encoding = 'base64';
             return Base64EncodedStream::fromString($text, $this->lineLength, $this->lineBreak);
         }