diff --git a/src/utils/__tests__/PhutilUtilsTestCase.php b/src/utils/__tests__/PhutilUtilsTestCase.php
--- a/src/utils/__tests__/PhutilUtilsTestCase.php
+++ b/src/utils/__tests__/PhutilUtilsTestCase.php
@@ -505,6 +505,11 @@
 
   public function testPhutilJSONDecode() {
     $valid_cases = array(
+      'null' => null,
+      'false' => false,
+      'true' => true,
+      '"string"' => 'string',
+      '123' => 123,
       '{}' => array(),
       '[]' => array(),
       '[1, 2]' => array(1, 2),
@@ -517,11 +522,10 @@
     }
 
     $invalid_cases = array(
-      '',
-      '"a"',
+      'nil',
       '{,}',
-      'null',
-      '"null"',
+      '[,]',
+      '{',
     );
 
     foreach ($invalid_cases as $input) {
diff --git a/src/utils/utils.php b/src/utils/utils.php
--- a/src/utils/utils.php
+++ b/src/utils/utils.php
@@ -1046,7 +1046,7 @@
 function phutil_json_decode($string) {
   $result = @json_decode($string, true);
 
-  if (!is_array($result)) {
+  if ($result === null && $string !== 'null') {
     // Failed to decode the JSON. Try to use @{class:PhutilJSONParser} instead.
     // This will probably fail, but will throw a useful exception.
     $parser = new PhutilJSONParser();