diff --git a/composer.json b/composer.json
index 8f5429b..f8b7edf 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,8 @@
         }
     ],
     "require": {
-        "php": "~7.4.0 || ~8.0.0 || ~8.1.0"
+        "php": "~7.4.0 || ~8.0.0 || ~8.1.0",
+        "stella-maris/clock": "^0.1.4"
     },
     "require-dev": {
         "phpstan/extension-installer": "^1.1",
@@ -27,7 +28,6 @@
             "Beste\\Clock\\": "src/Clock"
         },
         "files": [
-            "src/psr-polyfill.php",
             "src/Clock.php"
         ]
     },
@@ -40,7 +40,10 @@
         "psr/clock-implementation": "1.0"
     },
     "config": {
-        "sort-packages": true
+        "sort-packages": true,
+        "allow-plugins": {
+            "phpstan/extension-installer": true
+        }
     },
     "scripts": {
         "test": [
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 2712cf2..58f5ef4 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -7,5 +7,3 @@ parameters:
 
 	tmpDir: .build/phpstan/
 
-	bootstrapFiles:
-		- ./src/psr-polyfill.php
diff --git a/src/Clock.php b/src/Clock.php
index 5693d1d..02d9f71 100644
--- a/src/Clock.php
+++ b/src/Clock.php
@@ -4,7 +4,7 @@ declare(strict_types=1);
 
 namespace Beste;
 
-use Psr\Clock\ClockInterface;
+use StellaMaris\Clock\ClockInterface;
 
 interface Clock extends ClockInterface
 {
diff --git a/src/Clock/FrozenClock.php b/src/Clock/FrozenClock.php
index 40f2895..f2bf651 100644
--- a/src/Clock/FrozenClock.php
+++ b/src/Clock/FrozenClock.php
@@ -7,7 +7,7 @@ namespace Beste\Clock;
 use Beste\Clock;
 use DateTimeImmutable;
 use DateTimeZone;
-use Psr\Clock\ClockInterface;
+use StellaMaris\Clock\ClockInterface;
 
 final class FrozenClock implements Clock
 {
diff --git a/src/Clock/MinuteClock.php b/src/Clock/MinuteClock.php
index 309545f..a7b5a31 100644
--- a/src/Clock/MinuteClock.php
+++ b/src/Clock/MinuteClock.php
@@ -6,7 +6,7 @@ namespace Beste\Clock;
 
 use Beste\Clock;
 use DateTimeImmutable;
-use Psr\Clock\ClockInterface;
+use StellaMaris\Clock\ClockInterface;
 
 final class MinuteClock implements Clock
 {
diff --git a/src/psr-polyfill.php b/src/psr-polyfill.php
deleted file mode 100644
index 1a96e74..0000000
--- a/src/psr-polyfill.php
+++ /dev/null
@@ -1,17 +0,0 @@
-<?php
-
-namespace Psr\Clock;
-
-if (class_exists('\Psr\Clock\ClockInterface')) {
-    return;
-}
-
-use DateTimeImmutable;
-
-interface ClockInterface
-{
-    /**
-     * Returns the current time as a DateTimeImmutable Object
-     */
-    public function now(): DateTimeImmutable;
-}
diff --git a/tests/Clock/FrozenClockTest.php b/tests/Clock/FrozenClockTest.php
index 42d5be8..af24b1a 100644
--- a/tests/Clock/FrozenClockTest.php
+++ b/tests/Clock/FrozenClockTest.php
@@ -7,7 +7,7 @@ namespace Beste\Clock\Tests;
 use Beste\Clock\FrozenClock;
 use DateTimeImmutable;
 use PHPUnit\Framework\TestCase;
-use Psr\Clock\ClockInterface;
+use StellaMaris\Clock\ClockInterface;
 
 /**
  * @internal
diff --git a/tests/Clock/MinuteClockTest.php b/tests/Clock/MinuteClockTest.php
index 729c0ac..baf55fb 100644
--- a/tests/Clock/MinuteClockTest.php
+++ b/tests/Clock/MinuteClockTest.php
@@ -7,7 +7,7 @@ namespace Beste\Clock\Tests;
 use Beste\Clock\MinuteClock;
 use DateTimeImmutable;
 use PHPUnit\Framework\TestCase;
-use Psr\Clock\ClockInterface;
+use StellaMaris\Clock\ClockInterface;
 
 /**
  * @internal