diff --git a/lib/BlockingDriver.php b/lib/BlockingDriver.php
index 98cc0ff..b5b4b3d 100644
--- a/lib/BlockingDriver.php
+++ b/lib/BlockingDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/BlockingHandle.php b/lib/BlockingHandle.php
index d27405b..1ada886 100644
--- a/lib/BlockingHandle.php
+++ b/lib/BlockingHandle.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/Driver.php b/lib/Driver.php
index acec2e7..9595fb4 100644
--- a/lib/Driver.php
+++ b/lib/Driver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/EioDriver.php b/lib/EioDriver.php
index 64b8db0..f48ab61 100644
--- a/lib/EioDriver.php
+++ b/lib/EioDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/EioHandle.php b/lib/EioHandle.php
index ff8af6d..0526080 100644
--- a/lib/EioHandle.php
+++ b/lib/EioHandle.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/FilesystemException.php b/lib/FilesystemException.php
index 4453fda..d66d0e9 100644
--- a/lib/FilesystemException.php
+++ b/lib/FilesystemException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/Handle.php b/lib/Handle.php
index fbf9b17..2d14a03 100644
--- a/lib/Handle.php
+++ b/lib/Handle.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/StatCache.php b/lib/StatCache.php
index 7a7dfab..e462756 100644
--- a/lib/StatCache.php
+++ b/lib/StatCache.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/UvDriver.php b/lib/UvDriver.php
index 4178e93..778b8dd 100644
--- a/lib/UvDriver.php
+++ b/lib/UvDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/UvHandle.php b/lib/UvHandle.php
index 25710b1..48d7877 100644
--- a/lib/UvHandle.php
+++ b/lib/UvHandle.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/lib/functions.php b/lib/functions.php
index 0b23ebc..be15262 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File;
 
diff --git a/test/BlockingDriverTest.php b/test/BlockingDriverTest.php
index 7bd0bb5..2fe510b 100644
--- a/test/BlockingDriverTest.php
+++ b/test/BlockingDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/BlockingHandleTest.php b/test/BlockingHandleTest.php
index 931f2cb..2898cba 100644
--- a/test/BlockingHandleTest.php
+++ b/test/BlockingHandleTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/DriverTest.php b/test/DriverTest.php
index b470fed..88c8dfb 100644
--- a/test/DriverTest.php
+++ b/test/DriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/EioDriverTest.php b/test/EioDriverTest.php
index 4c7aa3b..2393a28 100644
--- a/test/EioDriverTest.php
+++ b/test/EioDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/EioHandleTest.php b/test/EioHandleTest.php
index 9b6c485..319675d 100644
--- a/test/EioHandleTest.php
+++ b/test/EioHandleTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/Fixture.php b/test/Fixture.php
index bb9b16c..2241ef8 100644
--- a/test/Fixture.php
+++ b/test/Fixture.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/HandleTest.php b/test/HandleTest.php
index 7871381..9542573 100644
--- a/test/HandleTest.php
+++ b/test/HandleTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
@@ -45,7 +45,7 @@ abstract class HandleTest extends \PHPUnit_Framework_TestCase {
             $position = 0;
 
             $stat = (yield file\stat(__FILE__));
-            $chunkSize = \floor(($stat["size"] / 5));
+            $chunkSize = (int) \floor(($stat["size"] / 5));
 
             while (!$handle->eof()) {
                 $chunk = (yield $handle->read($chunkSize));
diff --git a/test/UvDriverTest.php b/test/UvDriverTest.php
index 6892d85..78e6672 100644
--- a/test/UvDriverTest.php
+++ b/test/UvDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;
 
diff --git a/test/UvHandleTest.php b/test/UvHandleTest.php
index a9e518a..8613fee 100644
--- a/test/UvHandleTest.php
+++ b/test/UvHandleTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types = 1);
 
 namespace Amp\File\Test;