diff --git a/lib/Emitter.php b/lib/Emitter.php
index b2a60ce..5e07407 100644
--- a/lib/Emitter.php
+++ b/lib/Emitter.php
@@ -11,14 +11,13 @@ final class Emitter implements Observable {
     public function __construct(callable $emitter) {
         $this->init();
     
-        /**
-         * @param mixed $value
-         *
-         * @return \Interop\Async\Awaitable
-         */
-        $emit = function ($value) {
-            return $this->emit($value);
-        };
+        if (PHP_VERSION_ID >= 70100) {
+            $emit = \Closure::fromCallable([$this, 'emit']);
+        } else {
+            $emit = function ($value) {
+                return $this->emit($value);
+            };
+        }
         
         $result = $emitter($emit);
 
diff --git a/lib/Internal/Producer.php b/lib/Internal/Producer.php
index e46ab68..f56cccd 100644
--- a/lib/Internal/Producer.php
+++ b/lib/Internal/Producer.php
@@ -50,9 +50,14 @@ trait Producer {
      */
     private function init() {
         $this->waiting = new Future;
-        $this->unsubscribe = function ($id) {
-            $this->unsubscribe($id);
-        };
+
+        if (PHP_VERSION_ID >= 70100) {
+            $this->unsubscribe = \Closure::fromCallable([$this, 'unsubscribe']);
+        } else {
+            $this->unsubscribe = function ($id) {
+                $this->unsubscribe($id);
+            };
+        }
     }
 
     /**