diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0bfe424..93d04a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [Unreleased]
+
+### Fixed
+
+- PHP `8.4` deprecations
+
 ## 4.4.0 - 2024-03-10
 
 ### Changed
diff --git a/src/Continuation.php b/src/Continuation.php
index aa85ee2..7ac3e6a 100644
--- a/src/Continuation.php
+++ b/src/Continuation.php
@@ -23,7 +23,7 @@ private function __construct(
         Client $client,
         mixed $carry,
         bool $closed = false,
-        Message $response = null,
+        ?Message $response = null,
         bool $stop = false,
     ) {
         $this->client = $client;
diff --git a/src/Factory.php b/src/Factory.php
index 857576f..7f219db 100644
--- a/src/Factory.php
+++ b/src/Factory.php
@@ -11,8 +11,8 @@ final class Factory
 {
     public static function build(
         OperatingSystem $os,
-        Path $sockets = null,
-        ElapsedPeriod $heartbeat = null,
+        ?Path $sockets = null,
+        ?ElapsedPeriod $heartbeat = null,
     ): IPC {
         $sockets ??= $os->status()->tmp()->resolve(Path::of('innmind/ipc/'));
         $heartbeat ??= new ElapsedPeriod(1000); // default to 1 second
diff --git a/src/IPC.php b/src/IPC.php
index e7a1d27..0cc0ef8 100644
--- a/src/IPC.php
+++ b/src/IPC.php
@@ -25,6 +25,6 @@ public function exist(Process\Name $name): bool;
     /**
      * @return Maybe<Process>
      */
-    public function wait(Process\Name $name, ElapsedPeriod $timeout = null): Maybe;
-    public function listen(Process\Name $self, ElapsedPeriod $timeout = null): Server;
+    public function wait(Process\Name $name, ?ElapsedPeriod $timeout = null): Maybe;
+    public function listen(Process\Name $self, ?ElapsedPeriod $timeout = null): Server;
 }
diff --git a/src/IPC/Unix.php b/src/IPC/Unix.php
index 0702ef9..0d9d2d4 100644
--- a/src/IPC/Unix.php
+++ b/src/IPC/Unix.php
@@ -99,7 +99,7 @@ public function exist(Process\Name $name): bool
         return $this->filesystem->contains(FileName::of("{$name->toString()}.sock"));
     }
 
-    public function wait(Process\Name $name, ElapsedPeriod $timeout = null): Maybe
+    public function wait(Process\Name $name, ?ElapsedPeriod $timeout = null): Maybe
     {
         $start = $this->clock->now();
 
@@ -118,7 +118,7 @@ public function wait(Process\Name $name, ElapsedPeriod $timeout = null): Maybe
         return $this->get($name);
     }
 
-    public function listen(Process\Name $self, ElapsedPeriod $timeout = null): Server
+    public function listen(Process\Name $self, ?ElapsedPeriod $timeout = null): Server
     {
         return new Server\Unix(
             $this->sockets,
diff --git a/src/Process.php b/src/Process.php
index 6f873cf..e1b0d11 100644
--- a/src/Process.php
+++ b/src/Process.php
@@ -24,7 +24,7 @@ public function send(Sequence $messages): Maybe;
     /**
      * @return Maybe<Message>
      */
-    public function wait(ElapsedPeriod $timeout = null): Maybe;
+    public function wait(?ElapsedPeriod $timeout = null): Maybe;
 
     /**
      * @return Maybe<SideEffect> Returns nothing when couldn't close the connection properly
diff --git a/src/Process/Unix.php b/src/Process/Unix.php
index f2f89db..2976945 100644
--- a/src/Process/Unix.php
+++ b/src/Process/Unix.php
@@ -101,7 +101,7 @@ public function send(Sequence $messages): Maybe
         );
     }
 
-    public function wait(ElapsedPeriod $timeout = null): Maybe
+    public function wait(?ElapsedPeriod $timeout = null): Maybe
     {
         do {
             if ($this->closed()) {
@@ -209,7 +209,7 @@ private function cut(): Maybe
         return $this->socket->close()->maybe();
     }
 
-    private function timedout(ElapsedPeriod $timeout = null): bool
+    private function timedout(?ElapsedPeriod $timeout = null): bool
     {
         if ($timeout === null) {
             return false;
diff --git a/src/Server/Unix.php b/src/Server/Unix.php
index 0863809..0397197 100644
--- a/src/Server/Unix.php
+++ b/src/Server/Unix.php
@@ -41,7 +41,7 @@ public function __construct(
         Signals $signals,
         Address $address,
         ElapsedPeriod $heartbeat,
-        ElapsedPeriod $timeout = null,
+        ?ElapsedPeriod $timeout = null,
     ) {
         $this->sockets = $sockets;
         $this->protocol = $protocol;