diff --git a/src/Composer/Json/JsonManipulator.php b/src/Composer/Json/JsonManipulator.php
index 40c0c09a2..8fe6a9f0a 100644
--- a/src/Composer/Json/JsonManipulator.php
+++ b/src/Composer/Json/JsonManipulator.php
@@ -22,7 +22,7 @@ class JsonManipulator
     private static $DEFINES = '(?(DEFINE)
        (?<number>   -? (?= [1-9]|0(?!\d) ) \d+ (\.\d+)? ([eE] [+-]? \d+)? )
        (?<boolean>   true | false | null )
-       (?<string>    " ([^"\\\\]* | \\\\ ["\\\\bfnrt\/] | \\\\ u [0-9a-f]{4} )* " )
+       (?<string>    " ([^"\\\\]* | \\\\ ["\\\\bfnrt\/] | \\\\ u [0-9A-Fa-f]{4} )* " )
        (?<array>     \[  (?:  (?&json) \s* (?: , (?&json) \s* )*  )?  \s* \] )
        (?<pair>      \s* (?&string) \s* : (?&json) \s* )
        (?<object>    \{  (?:  (?&pair)  (?: , (?&pair)  )*  )?  \s* \} )
diff --git a/tests/Composer/Test/Json/JsonManipulatorTest.php b/tests/Composer/Test/Json/JsonManipulatorTest.php
index 05de454ca..d8bc7c200 100644
--- a/tests/Composer/Test/Json/JsonManipulatorTest.php
+++ b/tests/Composer/Test/Json/JsonManipulatorTest.php
@@ -2374,6 +2374,26 @@ class JsonManipulatorTest extends TestCase
         "package/a": "*"
     }
 }
+', $manipulator->getContents());
+    }
+
+    public function testEscapedUnicodeDoesNotCauseBacktrackLimitErrorGithubIssue8131()
+    {
+        $manipulator = new JsonManipulator('{
+  "description": "Some U\u00F1icode",
+  "require": {
+    "foo/bar": "^1.0"
+  }
+}');
+
+        $this->assertTrue($manipulator->addLink('require', 'foo/baz', '^1.0'));
+        $this->assertEquals('{
+  "description": "Some U\u00F1icode",
+  "require": {
+    "foo/bar": "^1.0",
+    "foo/baz": "^1.0"
+  }
+}
 ', $manipulator->getContents());
     }
 }