Regex does return null every second time it is executed

import QtQuick 2.0 
import QtTest 1.0

TestCase {
    name: "Regexp"



    function test_match() {
        var regexp = /CC_(\d+)/g;
        var data = "O__131458;OC_131444;C__131426;CC_131428;";

        verify(regexp.exec(data) !== null, "test regexp1");
        verify(regexp.exec(data) !== null, "test regexp2");
        verify(regexp.exec(data) !== null, "test regexp3");
        verify(regexp.exec(data) !== null, "test regexp4");
        verify(regexp.exec(data) !== null, "test regexp5");
    }
}

********* Start testing of qmltest *********
Config: Using QtTest library 5.6.2, Qt 5.6.2 (i386-little_endian-ilp32 shared (dynamic) debug build; by MSVC 2013)
PASS   : qmltest::Regexp::initTestCase()
FAIL!  : qmltest::Regexp::test_match() 'test regexp2' returned FALSE. ()
C:\projects\gitRS\PROG-5.00\kratos\kratos\build-src-Desktop_Qt_5_6_2_MSVC2013_32bit-Debug\external_build\test\QmlTest\Debug\qml\test\general\tst_Regexp.qml(14) : failure location
PASS   : qmltest::Regexp::cleanupTestCase()
Totals: 2 passed, 1 failed, 0 skipped, 0 blacklisted
********* Finished testing of qmltest *********