diff --git a/src/Tracy/Dumper.php b/src/Tracy/Dumper.php
index 9c0643307..495a8c186 100644
--- a/src/Tracy/Dumper.php
+++ b/src/Tracy/Dumper.php
@@ -218,9 +218,8 @@ private static function dumpArray(&$var, array $options, int $level): string
 			foreach ($var as $k => &$v) {
 				if ($k !== $marker) {
 					$hide = is_string($k) && isset($options[self::KEYS_TO_HIDE][strtolower($k)]) ? self::HIDDEN_VALUE : null;
-					$k = is_int($k) || preg_match('#^\w{1,50}\z#', $k) ? $k : '"' . Helpers::escapeHtml(self::encodeString($k, $options[self::TRUNCATE])) . '"';
 					$out .= '<span class="tracy-dump-indent">   ' . str_repeat('|  ', $level) . '</span>'
-						. '<span class="tracy-dump-key">' . $k . '</span> => '
+						. '<span class="tracy-dump-key">' . Helpers::escapeHtml(self::encodeKey($k, $options)) . '</span> => '
 						. ($hide ? self::dumpString($hide, $options) : self::dumpVar($v, $options, $level + 1));
 				}
 			}
@@ -275,9 +274,8 @@ private static function dumpObject(&$var, array $options, int $level): string
 					$k = substr($k, strrpos($k, "\x00") + 1);
 				}
 				$hide = is_string($k) && isset($options[self::KEYS_TO_HIDE][strtolower($k)]) ? self::HIDDEN_VALUE : null;
-				$k = is_int($k) || preg_match('#^\w{1,50}\z#', $k) ? $k : '"' . Helpers::escapeHtml(self::encodeString($k, $options[self::TRUNCATE])) . '"';
 				$out .= '<span class="tracy-dump-indent">   ' . str_repeat('|  ', $level) . '</span>'
-					. '<span class="tracy-dump-key">' . $k . "</span>$vis => "
+					. '<span class="tracy-dump-key">' . Helpers::escapeHtml(self::encodeKey($k, $options)) . "</span>$vis => "
 					. ($hide ? self::dumpString($hide, $options) : self::dumpVar($v, $options, $level + 1));
 			}
 			array_pop($list);
@@ -335,8 +333,7 @@ private static function toJson(&$var, array $options, int $level = 0)
 			foreach ($var as $k => &$v) {
 				if ($k !== $marker) {
 					$hide = is_string($k) && isset($options[self::KEYS_TO_HIDE][strtolower($k)]);
-					$k = is_int($k) || preg_match('#^\w{1,50}\z#', $k) ? $k : '"' . self::encodeString($k, $options[self::TRUNCATE]) . '"';
-					$res[] = [$k, $hide ? self::HIDDEN_VALUE : self::toJson($v, $options, $level + 1)];
+					$res[] = [self::encodeKey($k, $options), $hide ? self::HIDDEN_VALUE : self::toJson($v, $options, $level + 1)];
 				}
 			}
 			unset($var[$marker]);
@@ -374,8 +371,7 @@ private static function toJson(&$var, array $options, int $level = 0)
 						$k = substr($k, strrpos($k, "\x00") + 1);
 					}
 					$hide = is_string($k) && isset($options[self::KEYS_TO_HIDE][strtolower($k)]);
-					$k = is_int($k) || preg_match('#^\w{1,50}\z#', $k) ? $k : '"' . self::encodeString($k, $options[self::TRUNCATE]) . '"';
-					$obj['items'][] = [$k, $hide ? self::HIDDEN_VALUE : self::toJson($v, $options, $level + 1), $vis];
+					$obj['items'][] = [self::encodeKey($k, $options), $hide ? self::HIDDEN_VALUE : self::toJson($v, $options, $level + 1), $vis];
 				}
 			}
 			return ['object' => $obj['id']];
@@ -457,6 +453,18 @@ public static function encodeString(string $s, int $maxLength = null): string
 	}
 
 
+	/**
+	 * @param  int|string  $k
+	 * @return int|string
+	 */
+	private static function encodeKey($key, array $options)
+	{
+		return is_int($key) || preg_match('#^[!\#$%&()*+,./0-9:;<=>?@A-Z[\]^_`a-z{|}~-]{1,50}\z#', $key)
+			? $key
+			: '"' . self::encodeString($key, $options[self::TRUNCATE]) . '"';
+	}
+
+
 	/**
 	 * @param  object  $obj
 	 */
diff --git a/tests/Tracy/Dumper.keys.phpt b/tests/Tracy/Dumper.keys.phpt
new file mode 100644
index 000000000..cbbd6b3c1
--- /dev/null
+++ b/tests/Tracy/Dumper.keys.phpt
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+use Tester\Assert;
+use Tracy\Dumper;
+
+
+require __DIR__ . '/../bootstrap.php';
+
+
+$keys = [
+	'' => 0,
+	'"' => 0,
+	"'" => 0,
+	'key' => 0,
+	' key' => 0,
+	'key ' => 0,
+	0 => 0,
+	'01' => 0,
+];
+
+Assert::match('array (%i%)
+   "" => 0
+   """ => 0
+   "\'" => 0
+   key => 0
+   " key" => 0
+   "key " => 0
+   0 => 0
+   01 => 0
+', Dumper::toText($keys));
+
+Assert::match('stdClass #%a%
+   "" => 0
+   """ => 0
+   "\'" => 0
+   key => 0
+   " key" => 0
+   "key " => 0
+   0 => 0
+   01 => 0
+', Dumper::toText((object) $keys));
+
+Assert::match(
+	'<pre class="tracy-dump" data-tracy-dump=\'{"object":"01"}\'></pre>',
+	Dumper::toHtml((object) $keys, [Dumper::LIVE => true])
+);
+
+Assert::same([
+	'01' => [
+		'name' => 'stdClass',
+		'editor' => null,
+		'items' => [
+			['""', 0, 0],
+			['"""', 0, 0],
+			['"\'"', 0, 0],
+			['key', 0, 0],
+			['" key"', 0, 0],
+			['"key "', 0, 0],
+			[0, 0, 0],
+			['01', 0, 0],
+		],
+	],
+], Dumper::fetchLiveData());
diff --git a/tests/Tracy/Dumper.objectExporters.phpt b/tests/Tracy/Dumper.objectExporters.phpt
index a226f5943..5cee5d23c 100644
--- a/tests/Tracy/Dumper.objectExporters.phpt
+++ b/tests/Tracy/Dumper.objectExporters.phpt
@@ -39,9 +39,9 @@ $obj = unserialize('O:1:"Y":7:{s:1:"a";N;s:1:"b";i:2;s:4:"' . "\0" . '*' . "\0"
 Assert::match('__PHP_Incomplete_Class #%a%
    className => "Y"
    private => array (3)
-   |  "Y::$e" => null
-   |  "Y::$i" => "bar" (3)
-   |  "X::$i" => "foo" (3)
+   |  Y::$e => null
+   |  Y::$i => "bar" (3)
+   |  X::$i => "foo" (3)
    protected => array (2)
    |  c => null
    |  d => "d"