diff --git a/src/BSON/Regex.c b/src/BSON/Regex.c
index efa6d58d2..b4b7d6d31 100644
--- a/src/BSON/Regex.c
+++ b/src/BSON/Regex.c
@@ -54,16 +54,20 @@ static bool php_phongo_regex_init(php_phongo_regex_t *intern, const char *patter
 		phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT TSRMLS_CC, "Pattern cannot contain null bytes");
 		return false;
 	}
-
-	if (strlen(flags) != flags_len) {
-		phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT TSRMLS_CC, "Flags cannot contain null bytes");
-		return false;
-	}
-
 	intern->pattern = estrndup(pattern, pattern_len);
 	intern->pattern_len = pattern_len;
-	intern->flags = estrndup(flags, flags_len);
-	intern->flags_len = flags_len;
+
+	if (flags) {
+		if (strlen(flags) != flags_len) {
+			phongo_throw_exception(PHONGO_ERROR_INVALID_ARGUMENT TSRMLS_CC, "Flags cannot contain null bytes");
+			return false;
+		}
+		intern->flags = estrndup(flags, flags_len);
+		intern->flags_len = flags_len;
+	} else {
+		intern->flags = estrdup("");
+		intern->flags_len = 0;
+	}
 
 	return true;
 }
@@ -92,7 +96,7 @@ static bool php_phongo_regex_init_from_hash(php_phongo_regex_t *intern, HashTabl
 	return false;
 }
 
-/* {{{ proto void Regex::__construct(string $pattern, string $flags)
+/* {{{ proto void Regex::__construct(string $pattern [, string $flags])
    Constructs a new BSON regular expression type. */
 PHP_METHOD(Regex, __construct)
 {
@@ -100,14 +104,14 @@ PHP_METHOD(Regex, __construct)
 	zend_error_handling       error_handling;
 	char                     *pattern;
 	phongo_zpp_char_len       pattern_len;
-	char                     *flags;
-	phongo_zpp_char_len       flags_len;
+	char                     *flags = NULL;
+	phongo_zpp_char_len       flags_len = 0;
 
 
 	zend_replace_error_handling(EH_THROW, phongo_exception_from_phongo_domain(PHONGO_ERROR_INVALID_ARGUMENT), &error_handling TSRMLS_CC);
 	intern = Z_REGEX_OBJ_P(getThis());
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss", &pattern, &pattern_len, &flags, &flags_len) == FAILURE) {
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|s", &pattern, &pattern_len, &flags, &flags_len) == FAILURE) {
 		zend_restore_error_handling(&error_handling TSRMLS_CC);
 		return;
 	}
diff --git a/tests/bson/bson-regex-003.phpt b/tests/bson/bson-regex-003.phpt
new file mode 100644
index 000000000..9de943e02
--- /dev/null
+++ b/tests/bson/bson-regex-003.phpt
@@ -0,0 +1,36 @@
+--TEST--
+MongoDB\BSON\Regex with flags omitted
+--FILE--
+<?php
+
+require_once __DIR__ . '/../utils/tools.php';
+
+$regexp = new MongoDB\BSON\Regex("regexp");
+printf("Pattern: %s\n", $regexp->getPattern());
+printf("Flags: %s\n", $regexp->getFlags());
+printf("String representation: %s\n", $regexp);
+
+$tests = array(
+    array("regex" => $regexp),
+);
+
+foreach($tests as $n => $test) {
+    $s = fromPHP($test);
+    echo "Test#{$n} ", $json = toJSON($s), "\n";
+    $bson = fromJSON($json);
+    $testagain = toPHP($bson);
+    var_dump(toJSON(fromPHP($test)), toJSON(fromPHP($testagain)));
+    var_dump((object)$test == (object)$testagain);
+}
+?>
+===DONE===
+<?php exit(0); ?>
+--EXPECTF--
+Pattern: regexp
+Flags: 
+String representation: /regexp/
+Test#0 { "regex" : { "$regex" : "regexp", "$options" : "" } }
+string(54) "{ "regex" : { "$regex" : "regexp", "$options" : "" } }"
+string(54) "{ "regex" : { "$regex" : "regexp", "$options" : "" } }"
+bool(true)
+===DONE===
diff --git a/tests/bson/bson-regex-004.phpt b/tests/bson/bson-regex-004.phpt
new file mode 100644
index 000000000..0f6cca88e
--- /dev/null
+++ b/tests/bson/bson-regex-004.phpt
@@ -0,0 +1,20 @@
+--TEST--
+MongoDB\BSON\Regex debug handler with flags omitted
+--FILE--
+<?php
+
+$regex = new MongoDB\BSON\Regex('regexp');
+
+var_dump($regex);
+
+?>
+===DONE===
+<?php exit(0); ?>
+--EXPECTF--
+object(MongoDB\BSON\Regex)#%d (%d) {
+  ["pattern"]=>
+  string(6) "regexp"
+  ["flags"]=>
+  string(0) ""
+}
+===DONE===
diff --git a/tests/bson/bson-regex-serialization-002.phpt b/tests/bson/bson-regex-serialization-002.phpt
new file mode 100644
index 000000000..ea03996e5
--- /dev/null
+++ b/tests/bson/bson-regex-serialization-002.phpt
@@ -0,0 +1,27 @@
+--TEST--
+MongoDB\BSON\Regex serialization with flags omitted
+--FILE--
+<?php
+
+var_dump($regex = new MongoDB\BSON\Regex('regexp'));
+var_dump($s = serialize($regex));
+var_dump(unserialize($s));
+
+?>
+===DONE===
+<?php exit(0); ?>
+--EXPECTF--
+object(MongoDB\BSON\Regex)#%d (%d) {
+  ["pattern"]=>
+  string(6) "regexp"
+  ["flags"]=>
+  string(0) ""
+}
+string(76) "O:18:"MongoDB\BSON\Regex":2:{s:7:"pattern";s:6:"regexp";s:5:"flags";s:0:"";}"
+object(MongoDB\BSON\Regex)#%d (%d) {
+  ["pattern"]=>
+  string(6) "regexp"
+  ["flags"]=>
+  string(0) ""
+}
+===DONE===