diff --git a/src/Monolog/Formatter/NormalizerFormatter.php b/src/Monolog/Formatter/NormalizerFormatter.php
index 46bf41b3..6b5ef5fb 100644
--- a/src/Monolog/Formatter/NormalizerFormatter.php
+++ b/src/Monolog/Formatter/NormalizerFormatter.php
@@ -150,9 +150,44 @@ class NormalizerFormatter implements FormatterInterface
         }
 
         if (version_compare(PHP_VERSION, '5.4.0', '>=')) {
-            return json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
+            $json = json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
+        } else {
+            $json = json_encode($data);
         }
 
-        return json_encode($data);
+        if ($json === false) {
+            $this->throwEncodeError(json_last_error(), $data);
+        }
+
+        return $json;
+    }
+
+    /**
+     * Throws an exception according to a given code with a customized message
+     *
+     * @param int   $code return code of json_last_error function
+     * @param mixed $data data that was meant to be encoded
+     * @throws \RuntimeException
+     */
+    private function throwEncodeError($code, $data)
+    {
+        switch ($code) {
+            case JSON_ERROR_DEPTH:
+                $msg = 'Maximum stack depth exceeded';
+                break;
+            case JSON_ERROR_STATE_MISMATCH:
+                $msg = 'Underflow or the modes mismatch';
+                break;
+            case JSON_ERROR_CTRL_CHAR:
+                $msg = 'Unexpected control character found';
+                break;
+            case JSON_ERROR_UTF8:
+                $msg = 'Malformed UTF-8 characters, possibly incorrectly encoded';
+                break;
+            default:
+                $msg = 'Unknown error';
+        }
+
+        throw new \RuntimeException('JSON encoding failed: '.$msg.'. Encoding: '.var_export($data, true));
     }
 }
diff --git a/tests/Monolog/Formatter/NormalizerFormatterTest.php b/tests/Monolog/Formatter/NormalizerFormatterTest.php
index 4ffeded0..83c45ca6 100644
--- a/tests/Monolog/Formatter/NormalizerFormatterTest.php
+++ b/tests/Monolog/Formatter/NormalizerFormatterTest.php
@@ -174,6 +174,17 @@ class NormalizerFormatterTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals(@json_encode(array($resource)), $res);
     }
 
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testThrowsOnInvalidEncoding()
+    {
+        $formatter = new NormalizerFormatter();
+        $reflMethod = new \ReflectionMethod($formatter, 'toJson');
+        $reflMethod->setAccessible(true);
+        $res = $reflMethod->invoke($formatter, array('message' => utf8_decode('öü')));
+    }
+
     public function testExceptionTraceWithArgs()
     {
         if (defined('HHVM_VERSION')) {