diff --git a/src/JsonSchema/Constraints/Object.php b/src/JsonSchema/Constraints/Object.php
index cbee0b5e..e9fc29e5 100644
--- a/src/JsonSchema/Constraints/Object.php
+++ b/src/JsonSchema/Constraints/Object.php
@@ -82,7 +82,11 @@ public function validateElement($element, $matches, $objectDefinition = null, $p
 
             // additional properties defined
             if (!in_array($i, $matches) && $additionalProp && !$definition) {
-                $this->checkUndefined($value, $additionalProp, $path, $i);
+                if ($additionalProp === true) {
+                    $this->checkUndefined($value, null, $path, $i);
+                } else {
+                    $this->checkUndefined($value, $additionalProp, $path, $i);
+                }
             }
 
             // property requires presence of another
diff --git a/tests/JsonSchema/Tests/Constraints/AdditionalPropertiesTest.php b/tests/JsonSchema/Tests/Constraints/AdditionalPropertiesTest.php
index a0c13ea6..9df7ae39 100644
--- a/tests/JsonSchema/Tests/Constraints/AdditionalPropertiesTest.php
+++ b/tests/JsonSchema/Tests/Constraints/AdditionalPropertiesTest.php
@@ -124,6 +124,19 @@ public function getValidTests()
                   },
                   "additionalProperties": {"type":"string"}
                 }'
+            ),
+            array(
+                '{
+                  "prop":"1",
+                  "additionalProp":[]
+                }',
+                '{
+                  "type":"object",
+                  "properties":{
+                    "prop":{"type":"string"}
+                  },
+                  "additionalProperties": true
+                }'
             )
         );
     }