diff --git a/README.md b/README.md
index 63c06c5..c409ef5 100644
--- a/README.md
+++ b/README.md
@@ -70,8 +70,9 @@ optional arguments:
                         (key,value1:value2). Return warning if equality check
                         fails
   -Q [KEY_VALUE_LIST_CRITICAL [KEY_VALUE_LIST_CRITICAL ...]], --key_equals_critical [KEY_VALUE_LIST_CRITICAL [KEY_VALUE_LIST_CRITICAL ...]]
-                        Same as -q but return critical if equality check
-                        fails.
+                        Same as -q but return critical if equality check fails.
+  -u [KEY_VALUE_LIST_UNKNOWN [KEY_VALUE_LIST_UNKNOWN --key_equals_unknown [KEY_VALUE_LIST_UNKNOWN [KEY_VALUE_LIST_UNKNOWN ...]]
+                        Same as -Q but return unknown if equality check fails.
   -m [METRIC_LIST [METRIC_LIST ...]], --key_metric [METRIC_LIST [METRIC_LIST ...]]
                         Gathers the values of these keys (key[>alias],UnitOfMe
                         asure,WarnRange,CriticalRange,Min,Max) for Nagios
diff --git a/check_http_json.py b/check_http_json.py
index 011d689..2fbeddb 100755
--- a/check_http_json.py
+++ b/check_http_json.py
@@ -305,6 +305,12 @@ class JsonRuleProcessor:
             failure += self.checkExists(self.key_list_critical)
         return failure
 
+    def checkUnknown(self):
+        unknown = ''
+    	if self.rules.key_value_list_unknown != None:
+            unknown += self.checkEquality(self.rules.key_value_list_unknown)
+	return unknown
+
     def checkMetrics(self):
         """Return a Nagios specific performance metrics string given keys
         and parameter definitions"""
@@ -403,6 +409,10 @@ def parseArgs():
                         dest='key_value_list_critical', nargs='*',
                         help='''Same as -q but return critical if
                         equality check fails.''')
+    parser.add_argument('-u', '--key_equals_unknown',
+                        dest='key_value_list_unknown', nargs='*',
+                        help='''Same as -q but return unknown if
+                        equality check fails.''')
     parser.add_argument('-m', '--key_metric', dest='metric_list', nargs='*',
                         help='''Gathers the values of these keys (key[>alias],
                         UnitOfMeasure,WarnRange,CriticalRange,Min,Max) for
@@ -646,6 +656,7 @@ if __name__ == "__main__":
         nagios.append_warning(processor.checkWarning())
         nagios.append_critical(processor.checkCritical())
         nagios.append_metrics(processor.checkMetrics())
+        nagios.append_unknown(processor.checkUnknown())
     # Print Nagios specific string and exit appropriately
     print nagios.getMessage()
     exit(nagios.getCode())