diff --git a/src/Signer/Key.php b/src/Signer/Key.php
index 8a97e409..7b727aff 100644
--- a/src/Signer/Key.php
+++ b/src/Signer/Key.php
@@ -7,7 +7,9 @@
 
 namespace Lcobucci\JWT\Signer;
 
+use Exception;
 use InvalidArgumentException;
+use SplFileObject;
 
 /**
  * @author Luís Otávio Cobucci Oblonczyk <lcobucci@gmail.com>
@@ -54,17 +56,17 @@ private function setContent($content)
      *
      * @return string
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      */
     private function readFile($content)
     {
-        $file = substr($content, 7);
+        try {
+            $file = new SplFileObject(substr($content, 7));
 
-        if (!is_readable($file)) {
-            throw new \InvalidArgumentException('You must inform a valid key file');
+            return $file->fread($file->getSize());
+        } catch (Exception $exception) {
+            throw new InvalidArgumentException('You must inform a valid key file', 0, $exception);
         }
-
-        return file_get_contents($file);
     }
 
     /**
diff --git a/test/unit/Signer/KeyTest.php b/test/unit/Signer/KeyTest.php
index 0f75589d..58dd8e82 100644
--- a/test/unit/Signer/KeyTest.php
+++ b/test/unit/Signer/KeyTest.php
@@ -23,7 +23,10 @@ public function configureRootDir()
         vfsStream::setup(
             'root',
             null,
-            ['test.pem' => 'testing']
+            [
+                'test.pem' => 'testing',
+                'emptyFolder' => []
+            ]
         );
     }
 
@@ -70,6 +73,20 @@ public function constructShouldRaiseExceptionWhenFileDoesNotExists()
         new Key('file://' . vfsStream::url('root/test2.pem'));
     }
 
+    /**
+     * @test
+     *
+     * @expectedException \InvalidArgumentException
+     *
+     * @covers Lcobucci\JWT\Signer\Key::__construct
+     * @covers Lcobucci\JWT\Signer\Key::setContent
+     * @covers Lcobucci\JWT\Signer\Key::readFile
+     */
+    public function constructShouldRaiseExceptionWhenFileGetContentsFailed()
+    {
+        new Key('file://' . vfsStream::url('root/emptyFolder'));
+    }
+
     /**
      * @test
      *