diff --git a/lib/Loop/EvDriver.php b/lib/Loop/EvDriver.php
index 1f6175d..2f5d690 100644
--- a/lib/Loop/EvDriver.php
+++ b/lib/Loop/EvDriver.php
@@ -31,7 +31,7 @@ class EvDriver extends Driver
     private $signals = [];
 
     /** @var int Internal timestamp for now. */
-    private $now = 0;
+    private $now;
 
     /** @var bool */
     private $nowUpdateNeeded = false;
@@ -43,6 +43,8 @@ class EvDriver extends Driver
     {
         $this->handle = new \EvLoop;
         $this->nowOffset = (int) (\microtime(true) * self::MILLISEC_PER_SEC);
+        $this->now = \random_int(0, $this->nowOffset);
+        $this->nowOffset -= $this->now;
 
         if (self::$activeSignals === null) {
             self::$activeSignals = &$this->signals;
diff --git a/lib/Loop/EventDriver.php b/lib/Loop/EventDriver.php
index d6a5c7e..3f2402d 100644
--- a/lib/Loop/EventDriver.php
+++ b/lib/Loop/EventDriver.php
@@ -34,7 +34,7 @@ class EventDriver extends Driver
     private $nowUpdateNeeded = false;
 
     /** @var int Internal timestamp for now. */
-    private $now = 0;
+    private $now;
 
     /** @var int Loop time offset from microtime() */
     private $nowOffset;
@@ -43,6 +43,8 @@ class EventDriver extends Driver
     {
         $this->handle = new \EventBase;
         $this->nowOffset = (int) (\microtime(true) * self::MILLISEC_PER_SEC);
+        $this->now = \random_int(0, $this->nowOffset);
+        $this->nowOffset -= $this->now;
 
         if (self::$activeSignals === null) {
             self::$activeSignals = &$this->signals;
diff --git a/lib/Loop/NativeDriver.php b/lib/Loop/NativeDriver.php
index 9d7007f..501577c 100644
--- a/lib/Loop/NativeDriver.php
+++ b/lib/Loop/NativeDriver.php
@@ -34,7 +34,7 @@ class NativeDriver extends Driver
     private $nowUpdateNeeded = false;
 
     /** @var int Internal timestamp for now. */
-    private $now = 0;
+    private $now;
 
     /** @var int Loop time offset from microtime() */
     private $nowOffset;
@@ -47,6 +47,8 @@ class NativeDriver extends Driver
         $this->timerQueue = new \SplPriorityQueue();
         $this->signalHandling = \extension_loaded("pcntl");
         $this->nowOffset = (int) (\microtime(true) * self::MILLISEC_PER_SEC);
+        $this->now = \random_int(0, $this->nowOffset);
+        $this->nowOffset -= $this->now;
     }
 
     /**
@@ -126,6 +128,10 @@ class NativeDriver extends Driver
                         // Execute the timer.
                         $result = ($watcher->callback)($id, $watcher->data);
 
+                        if ($result === null) {
+                            continue;
+                        }
+
                         if ($result instanceof \Generator) {
                             $result = new Coroutine($result);
                         }