diff --git a/lib/LibeventReactor.php b/lib/LibeventReactor.php
index <HASH>..<HASH> 100755
--- a/lib/LibeventReactor.php
+++ b/lib/LibeventReactor.php
@@ -64,9 +64,9 @@ class LibeventReactor implements SignalReactor {
             );
         }
 
-        $delay = $executeAt - $now;
+        $msDelay = ($executeAt - $now) * $this->resolution;
 
-        return $this->once($callback, $delay);
+        return $this->once($callback, $msDelay);
     }
 
     public function immediately(callable $callback) {
diff --git a/lib/NativeReactor.php b/lib/NativeReactor.php
index <HASH>..<HASH> 100755
--- a/lib/NativeReactor.php
+++ b/lib/NativeReactor.php
@@ -153,9 +153,9 @@ class NativeReactor implements Reactor {
             );
         }
 
-        $delay = $executeAt - $now;
+        $msDelay = ($executeAt - $now) * $this->resolution;
 
-        return $this->once($callback, $delay);
+        return $this->once($callback, $msDelay);
     }
 
     public function immediately(callable $callback) {
Fix broken Reactor::at millisecond resolutions