diff --git a/src/Framework/Constraint/JsonMatches.php b/src/Framework/Constraint/JsonMatches.php
index c70edf2c30e..6e36cf5ee90 100644
--- a/src/Framework/Constraint/JsonMatches.php
+++ b/src/Framework/Constraint/JsonMatches.php
@@ -78,13 +78,13 @@ protected function matches($other): bool
     protected function fail($other, $description, ComparisonFailure $comparisonFailure = null): void
     {
         if ($comparisonFailure === null) {
-            [$error] = Json::canonicalize($other);
+            [$error, $recodedOther] = Json::canonicalize($other);
 
             if ($error) {
                 parent::fail($other, $description);
             }
 
-            [$error] = Json::canonicalize($this->value);
+            [$error, $recodedValue] = Json::canonicalize($this->value);
 
             if ($error) {
                 parent::fail($other, $description);
@@ -93,8 +93,8 @@ protected function fail($other, $description, ComparisonFailure $comparisonFailu
             $comparisonFailure = new ComparisonFailure(
                 \json_decode($this->value),
                 \json_decode($other),
-                Json::prettify($this->value),
-                Json::prettify($other),
+                Json::prettify($recodedValue),
+                Json::prettify($recodedOther),
                 false,
                 'Failed asserting that two json values are equal.'
             );
diff --git a/src/Util/Json.php b/src/Util/Json.php
index b73e5bb63cc..8e7c82c0e0a 100644
--- a/src/Util/Json.php
+++ b/src/Util/Json.php
@@ -23,7 +23,7 @@ final class Json
      */
     public static function prettify(string $json): string
     {
-        $decodedJson = \json_decode($json, true);
+        $decodedJson = \json_decode($json, false);
 
         if (\json_last_error()) {
             throw new Exception(
diff --git a/tests/unit/Framework/Constraint/JsonMatchesTest.php b/tests/unit/Framework/Constraint/JsonMatchesTest.php
index d515323002f..464a642bb67 100644
--- a/tests/unit/Framework/Constraint/JsonMatchesTest.php
+++ b/tests/unit/Framework/Constraint/JsonMatchesTest.php
@@ -46,7 +46,7 @@ public static function evaluateThrowsExpectationFailedExceptionWhenJsonIsValidBu
             'string type not equals number'           => ['{"age": "5"}', '{"age": 5}'],
             'string type not equals boolean'          => ['{"age": "true"}', '{"age": true}'],
             'string type not equals null'             => ['{"age": "null"}', '{"age": null}'],
-            'null field different from missing field' => ['{"present": true, "missing": null}', '{"present": true}'],
+            'null field different from missing field' => ['{"missing": null, "present": true}', '{"present": true}'],
             'array elements are ordered'              => ['["first", "second"]', '["second", "first"]'],
         ];
     }
@@ -127,6 +127,59 @@ public function testFailErrorWithValidValueAndInvalidOther(): void
                 <<<EOF
 Failed asserting that '{"Mascott":"Tux"}' matches JSON string "{"Mascott"::}".
 
+EOF
+                ,
+                TestFailure::exceptionToString($e)
+            );
+        }
+    }
+
+    public function testEmptyObjectNotConvertedToArrayInDiff(): void
+    {
+        $constraint = new JsonMatches('{"obj": {}, "val": 1}');
+
+        try {
+            $constraint->evaluate('{"obj": {}, "val": 2}', '', false);
+        } catch (ExpectationFailedException $e) {
+            $this->assertEquals(
+                <<<EOF
+Failed asserting that '{"obj": {}, "val": 2}' matches JSON string "{"obj": {}, "val": 1}".
+--- Expected
++++ Actual
+@@ @@
+ {
+     "obj": {},
+-    "val": 1
++    "val": 2
+ }
+
+EOF
+                ,
+                TestFailure::exceptionToString($e)
+            );
+        }
+    }
+
+    public function testObjectAreCanonicalizedInDiff(): void
+    {
+        $constraint = new JsonMatches('{"obj": {"x": 1, "y": 2}, "val": 1}');
+
+        try {
+            $constraint->evaluate('{"obj": {"y": 2, "x": 1}, "val": 2}', '', false);
+        } catch (ExpectationFailedException $e) {
+            $this->assertEquals(
+                <<<EOF
+Failed asserting that '{"obj": {"y": 2, "x": 1}, "val": 2}' matches JSON string "{"obj": {"x": 1, "y": 2}, "val": 1}".
+--- Expected
++++ Actual
+@@ @@
+         "x": 1,
+         "y": 2
+     },
+-    "val": 1
++    "val": 2
+ }
+
 EOF
                 ,
                 TestFailure::exceptionToString($e)