diff --git a/src/Util/PcntlTimeout.php b/src/Util/PcntlTimeout.php
index 4fd1ca6..88705f7 100644
--- a/src/Util/PcntlTimeout.php
+++ b/src/Util/PcntlTimeout.php
@@ -59,21 +59,22 @@ public function __construct(int $timeout)
      */
     public function timeBoxed(callable $code)
     {
-        $existingHandler = pcntl_signal_get_handler(\SIGALRM);
+        if (pcntl_alarm($this->timeout) !== 0) {
+            throw new LockAcquireException('Existing process alarm is not supported');
+        }
+
+        $origSignalHandler = pcntl_signal_get_handler(\SIGALRM);
 
-        $signal = pcntl_signal(\SIGALRM, function (): void {
+        $timeout = $this->timeout;
+        $signalHandlerFx = static function () use ($timeout): void {
             throw new DeadlineException(sprintf(
                 'Timebox hit deadline of %d seconds',
-                $this->timeout
+                $timeout
             ));
-        });
-        if (!$signal) {
-            throw new LockAcquireException('Could not install signal handler');
-        }
+        };
 
-        $oldAlarm = pcntl_alarm($this->timeout);
-        if ($oldAlarm !== 0) {
-            throw new LockAcquireException('Existing alarm was not expected');
+        if (!pcntl_signal(\SIGALRM, $signalHandlerFx)) {
+            throw new LockAcquireException('Failed to install signal handler');
         }
 
         try {
@@ -83,7 +84,7 @@ public function timeBoxed(callable $code)
             try {
                 pcntl_signal_dispatch();
             } finally {
-                pcntl_signal(\SIGALRM, $existingHandler);
+                pcntl_signal(\SIGALRM, $origSignalHandler);
             }
         }
     }
diff --git a/tests/Util/PcntlTimeoutTest.php b/tests/Util/PcntlTimeoutTest.php
index da6d690..9ed8794 100644
--- a/tests/Util/PcntlTimeoutTest.php
+++ b/tests/Util/PcntlTimeoutTest.php
@@ -48,16 +48,19 @@ public function testShouldNotTimeout(): void
      */
     public function testShouldFailOnExistingAlarm(): void
     {
+        $origSignalHandler = pcntl_signal_get_handler(\SIGALRM);
         try {
             pcntl_alarm(1);
             $timeout = new PcntlTimeout(1);
 
             $this->expectException(LockAcquireException::class);
+            $this->expectExceptionMessage('Existing process alarm is not supported');
             $timeout->timeBoxed(static function () {
                 sleep(1);
             });
         } finally {
             pcntl_alarm(0);
+            self::assertSame($origSignalHandler, pcntl_signal_get_handler(\SIGALRM));
         }
     }