diff --git a/src/JsonSchema/Constraints/UndefinedConstraint.php b/src/JsonSchema/Constraints/UndefinedConstraint.php
index c0337200..5f9d6bc8 100644
--- a/src/JsonSchema/Constraints/UndefinedConstraint.php
+++ b/src/JsonSchema/Constraints/UndefinedConstraint.php
@@ -166,7 +166,7 @@ protected function validateCommonProperties($value, $schema = null, $path = null
         }
 
         // Verify minimum and maximum number of properties
-        if (is_object($value)) {
+        if (is_object($value) && !($value instanceof UndefinedConstraint)) {
             if (isset($schema->minProperties)) {
                 if (count(get_object_vars($value)) < $schema->minProperties) {
                     $this->addError($path, "Must contain a minimum of " . $schema->minProperties . " properties", 'minProperties', array('minProperties' => $schema->minProperties,));
diff --git a/tests/JsonSchema/Tests/Constraints/MinItemsMaxItemsTest.php b/tests/JsonSchema/Tests/Constraints/MinItemsMaxItemsTest.php
index 1b477845..d40f6701 100644
--- a/tests/JsonSchema/Tests/Constraints/MinItemsMaxItemsTest.php
+++ b/tests/JsonSchema/Tests/Constraints/MinItemsMaxItemsTest.php
@@ -63,6 +63,98 @@ public function getValidTests()
                     "value":{"type":"array","minItems":2,"maxItems":4}
                   }
                 }'
+            ),
+            // Regression test for issue 215
+            array(
+                '{
+                  "campaign": 1,
+                  "offset": 0,
+                  "service_provider": 3,
+                  "include_hotel": false,
+                  "arrival": "2016-01-20",
+                  "departure": "2016-01-27",
+                  "session": "foobar",
+                  "ip": "127.0.0.1",
+                  "language_iso_code": "de",
+                  "travellers": [
+                    18,
+                    18,
+                    18
+                  ]
+                }',
+                '{
+                  "type": "object",
+                  "additionalProperties": false,
+                  "required": [
+                    "session",
+                    "include_hotel",
+                    "arrival",
+                    "departure",
+                    "ip",
+                    "travellers",
+                    "language_iso_code"
+                  ],
+                  "properties": {
+                    "session": {
+                      "type": "string"
+                    },
+                    "campaign": {
+                      "type": "integer"
+                    },
+                    "service_provider": {
+                      "type": "integer"
+                    },
+                    "include_hotel": {
+                      "type": "boolean"
+                    },
+                    "arrival": {
+                      "type": "string",
+                      "pattern": "^[0-9]{4}-[0-9]{2}-[0-9]{2}$"
+                    },
+                    "departure": {
+                      "type": "string",
+                      "pattern": "^[0-9]{4}-[0-9]{2}-[0-9]{2}$"
+                    },
+                    "ip": {
+                      "type": "string"
+                    },
+                    "offerId": {
+                      "type": "integer",
+                      "minimum": 1
+                    },
+                    "quiet": {
+                      "type": "boolean"
+                    },
+                    "language_iso_code": {
+                      "type": "string"
+                    },
+                    "travellers": {
+                      "type": "array",
+                      "minItems": 1,
+                      "maxItems": 16,
+                      "items": {
+                        "type": "integer"
+                      }
+                    },
+                    "rooms": {
+                      "type": "object",
+                      "additionalProperties": false,
+                      "minProperties": 1,
+                      "maxProperties": 2,
+                      "properties": {
+                        "size_1": {
+                          "type": "number"
+                        },
+                        "size_2": {
+                          "type": "number"
+                        }
+                      }
+                    },
+                    "offset": {
+                      "type": "integer"
+                    }
+                  }
+                }'
             )
         );
     }