diff --git a/phpseclib/Crypt/EC/Formats/Signature/IEEE.php b/phpseclib/Crypt/EC/Formats/Signature/IEEE.php
index 69139da4..cb98daa7 100644
--- a/phpseclib/Crypt/EC/Formats/Signature/IEEE.php
+++ b/phpseclib/Crypt/EC/Formats/Signature/IEEE.php
@@ -15,6 +15,8 @@
  * @link      http://phpseclib.sourceforge.net
  */
 
+declare(strict_types=1);
+
 namespace phpseclib3\Crypt\EC\Formats\Signature;
 
 use phpseclib3\Math\BigInteger;
@@ -51,12 +53,8 @@ abstract class IEEE
 
     /**
      * Returns a signature in the appropriate format
-     *
-     * @param \phpseclib3\Math\BigInteger $r
-     * @param \phpseclib3\Math\BigInteger $s
-     * @return string
      */
-    public static function save(BigInteger $r, BigInteger $s)
+    public static function save(BigInteger $r, BigInteger $s): string
     {
         $r = $r->toBytes();
         $s = $s->toBytes();
diff --git a/tests/Unit/Crypt/EC/KeyTest.php b/tests/Unit/Crypt/EC/KeyTest.php
index 6d1aeb18..8241d2d0 100644
--- a/tests/Unit/Crypt/EC/KeyTest.php
+++ b/tests/Unit/Crypt/EC/KeyTest.php
@@ -696,7 +696,7 @@ cN6W+k8UvGf+Y/lDWNbFitQocabsDUvSN0edHH3UKP5QPTz4cOlyIPMrXQ==
     /**
      * @group github1956
      */
-    public function testIEEESignature()
+    public function testIEEESignature(): void
     {
         $key = '{"alg":"ES256","crv":"P-256","ext":true,"key_ops":["verify"],"kty":"EC","x":"FKwqyGd4i2NAl8RUXCCBRCAIbcpeGyfyXwgA_AWHb8Y","y":"njxhw5O6zGVkBlcPDKYj0E-6VO1giHTUkJWBhgKNqd8"}';
         $key = PublicKeyLoader::load($key)->withSignatureFormat('IEEE')->withHash('sha384');
diff --git a/tests/Unit/Math/PrimeFieldTest.php b/tests/Unit/Math/PrimeFieldTest.php
index 5ddfa757..bda14e84 100644
--- a/tests/Unit/Math/PrimeFieldTest.php
+++ b/tests/Unit/Math/PrimeFieldTest.php
@@ -23,7 +23,7 @@ class PrimeFieldTest extends PhpseclibTestCase
         $num2->squareRoot();
     }
 
-    public function testPrimeFieldWithPrimeNumbers()
+    public function testPrimeFieldWithPrimeNumbers(): void
     {
         $a = new BigInteger('65', 10);
         $p = new BigInteger('127', 10);