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
@@ -513,24 +513,35 @@
   }
 
   public function testPhutilJSONDecode() {
-    $default = (object)array();
-
-    $cases = array(
+    $valid_cases = array(
       '{}' => array(),
       '[]' => array(),
-      '' => $default,
-      '"a"' => $default,
-      '{,}' => $default,
-      'null' => $default,
-      '"null"' => $default,
       '[1, 2]' => array(1, 2),
       '{"a":"b"}' => array('a' => 'b'),
     );
 
-    foreach ($cases as $input => $expect) {
-      $result = phutil_json_decode($input, $default);
+    foreach ($valid_cases as $input => $expect) {
+      $result = phutil_json_decode($input);
       $this->assertEqual($expect, $result, 'phutil_json_decode('.$input.')');
     }
+
+    $invalid_cases = array(
+      '',
+      '"a"',
+      '{,}',
+      'null',
+      '"null"',
+    );
+
+    foreach ($invalid_cases as $input) {
+      $caught = null;
+      try {
+        phutil_json_decode($input);
+      } catch (Exception $ex) {
+        $caught = $ex;
+      }
+      $this->assertTrue($caught instanceof PhutilJSONParserException);
+    }
   }
 
   public function testCensorCredentials() {
diff --git a/src/utils/utils.php b/src/utils/utils.php
--- a/src/utils/utils.php
+++ b/src/utils/utils.php
@@ -1046,21 +1046,22 @@
 
 
 /**
- * Decode a JSON dictionary, or return a default value if the input does not
- * decode or does not decode into a dictionary.
+ * Decode a JSON dictionary.
  *
  * @param   string    A string which ostensibly contains a JSON-encoded list or
  *                    dictionary.
- * @param   default?  Optional default value to return if the string does not
- *                    decode, or does not decode into a list or dictionary.
- * @return  mixed     Decoded list/dictionary, or default value if string
- *                    failed to decode.
+ * @return  mixed     Decoded list/dictionary.
  */
-function phutil_json_decode($string, $default = array()) {
+function phutil_json_decode($string) {
   $result = @json_decode($string, true);
+
   if (!is_array($result)) {
-    return $default;
+    // Failed to decode the JSON. Try to use @{class:PhutilJSONParser} instead.
+    // This will probably fail, but will throw a useful exception.
+    $parser = new PhutilJSONParser();
+    $result = $parser->parse($string);
   }
+
   return $result;
 }