diff --git a/lib/PhpParser/Node/Scalar/String_.php b/lib/PhpParser/Node/Scalar/String_.php
index 9c7bef2947..f284e980e0 100644
--- a/lib/PhpParser/Node/Scalar/String_.php
+++ b/lib/PhpParser/Node/Scalar/String_.php
@@ -116,7 +116,7 @@ public static function parseEscapeSequences(string $str, ?string $quote, bool $p
 
         $extra = '';
         if ($parseUnicodeEscape) {
-            $extra = '|u\{([0-9a-fA-F]+)\}';
+            $extra = '|u\{([0-9a-fA-F]+)\}|u\{';
         }
 
         return preg_replace_callback(
@@ -131,6 +131,9 @@ function ($matches) {
                     return chr(hexdec(substr($str, 1)));
                 }
                 if ('u' === $str[0]) {
+                    if (!isset($matches[2])) {
+                        throw new Error('Invalid UTF-8 codepoint escape sequence');
+                    }
                     // PHP 8.6 warns when hexdec() produces a float.
                     $dec = @hexdec($matches[2]);
                     // If it overflowed to float, treat as INT_MAX, it will throw an error anyway.
diff --git a/test/code/parser/scalar/unicodeEscape.test b/test/code/parser/scalar/unicodeEscape.test
index c672fb08f0..140fa89f73 100644
--- a/test/code/parser/scalar/unicodeEscape.test
+++ b/test/code/parser/scalar/unicodeEscape.test
@@ -86,3 +86,35 @@ Invalid UTF-8 codepoint escape sequence: Codepoint too large on line 2
 "\u{110000}";
 -----
 Invalid UTF-8 codepoint escape sequence: Codepoint too large on line 2
+-----
+<?php
+"\u{zz}";
+-----
+Invalid UTF-8 codepoint escape sequence on line 2
+-----
+<?php
+"\u{}";
+-----
+Invalid UTF-8 codepoint escape sequence on line 2
+-----
+<?php
+"\u{4z}";
+-----
+Invalid UTF-8 codepoint escape sequence on line 2
+-----
+<?php
+"\u{41";
+-----
+Invalid UTF-8 codepoint escape sequence on line 2
+-----
+<?php
+"\u{";
+-----
+Invalid UTF-8 codepoint escape sequence on line 2
+-----
+<?php
+<<<STR
+\u{}
+STR;
+-----
+Invalid UTF-8 codepoint escape sequence on line 4