diff --git a/psalm.xml b/psalm.xml
index 78df975..38edc2c 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -14,7 +14,7 @@
             <directory name="vendor" />
         </ignoreFiles>
     </projectFiles>
-    <disableExtensions>
-        <extension name="random" />
-    </disableExtensions>
+    <issueHandlers>
+        <UndefinedAttributeClass errorLevel="suppress" />
+    </issueHandlers>
 </psalm>
diff --git a/src/IP.php b/src/IP.php
index 8d0466d..4073e4c 100644
--- a/src/IP.php
+++ b/src/IP.php
@@ -22,6 +22,7 @@ final private function __construct(string $address)
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     final public static function v4(string $address): IPv4
     {
         if (!\filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV4)) {
@@ -35,6 +36,7 @@ final public static function v4(string $address): IPv4
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     final public static function v6(string $address): IPv6
     {
         if (!\filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV6)) {
@@ -45,6 +47,7 @@ final public static function v6(string $address): IPv6
         return new IPv6($address);
     }
 
+    #[\NoDiscard]
     final public function equals(self $self): bool
     {
         return $this->address === $self->address;
@@ -53,6 +56,7 @@ final public function equals(self $self): bool
     /**
      * @return non-empty-string
      */
+    #[\NoDiscard]
     final public function toString(): string
     {
         return $this->address;
diff --git a/src/IPv4.php b/src/IPv4.php
index 8d6dc44..c155989 100644
--- a/src/IPv4.php
+++ b/src/IPv4.php
@@ -16,6 +16,7 @@ final class IPv4 extends IP
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     public static function of(string $address): self
     {
         return IP::v4($address);
@@ -24,6 +25,7 @@ public static function of(string $address): self
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     public static function localhost(): self
     {
         return self::of('127.0.0.1');
@@ -34,6 +36,7 @@ public static function localhost(): self
      *
      * @return Maybe<self>
      */
+    #[\NoDiscard]
     public static function maybe(string $address): Maybe
     {
         return self::attempt($address)->maybe();
@@ -44,6 +47,7 @@ public static function maybe(string $address): Maybe
      *
      * @return Attempt<self>
      */
+    #[\NoDiscard]
     public static function attempt(string $address): Attempt
     {
         return Attempt::of(static fn() => self::of($address));
diff --git a/src/IPv6.php b/src/IPv6.php
index 034a826..a3a7aa3 100644
--- a/src/IPv6.php
+++ b/src/IPv6.php
@@ -16,6 +16,7 @@ final class IPv6 extends IP
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     public static function of(string $address): self
     {
         return IP::v6($address);
@@ -24,6 +25,7 @@ public static function of(string $address): self
     /**
      * @psalm-pure
      */
+    #[\NoDiscard]
     public static function localhost(): self
     {
         return self::of('::1');
@@ -34,6 +36,7 @@ public static function localhost(): self
      *
      * @return Maybe<self>
      */
+    #[\NoDiscard]
     public static function maybe(string $address): Maybe
     {
         return self::attempt($address)->maybe();
@@ -44,6 +47,7 @@ public static function maybe(string $address): Maybe
      *
      * @return Attempt<self>
      */
+    #[\NoDiscard]
     public static function attempt(string $address): Attempt
     {
         return Attempt::of(static fn() => self::of($address));
diff --git a/tests/IPv4Test.php b/tests/IPv4Test.php
index 636f0ea..8b65ae4 100644
--- a/tests/IPv4Test.php
+++ b/tests/IPv4Test.php
@@ -43,7 +43,7 @@ public function testThrowWhenInvalidFormat()
         $this->expectException(\DomainException::class);
         $this->expectExceptionMessage('localhost');
 
-        IPv4::of('localhost');
+        $_ = IPv4::of('localhost');
     }
 
     public function testThrowWhenOutOfBound()
@@ -51,7 +51,7 @@ public function testThrowWhenOutOfBound()
         $this->expectException(\DomainException::class);
         $this->expectExceptionMessage('256.0.0.1');
 
-        IPv4::of('256.0.0.1');
+        $_ = IPv4::of('256.0.0.1');
     }
 
     public function testMaybeReturnNothingForInvalidAddress()
diff --git a/tests/IPv6Test.php b/tests/IPv6Test.php
index abffa06..05487f1 100644
--- a/tests/IPv6Test.php
+++ b/tests/IPv6Test.php
@@ -43,7 +43,7 @@ public function testThrowWhenInvalidFormat()
         $this->expectException(\DomainException::class);
         $this->expectExceptionMessage('localhost');
 
-        IPv6::of('localhost');
+        $_ = IPv6::of('localhost');
     }
 
     public function testThrowWhenOutOfBound()
@@ -51,7 +51,7 @@ public function testThrowWhenOutOfBound()
         $this->expectException(\DomainException::class);
         $this->expectExceptionMessage('::z');
 
-        IPv6::of('::z');
+        $_ = IPv6::of('::z');
     }
 
     public function testMaybeReturnNothingForInvalidAddress()