--- a/testing/mozbase/mozinfo/mozinfo/mozinfo.py
+++ b/testing/mozbase/mozinfo/mozinfo/mozinfo.py
@@ -23,16 +23,39 @@ from .string_version import StringVersio
 class unknown(object):
     """marker class for unknown information"""
     def __nonzero__(self):
         return False
     def __str__(self):
         return 'UNKNOWN'
 unknown = unknown() # singleton
 
+def get_windows_version():
+    import ctypes
+    class OSVERSIONINFOEXW(ctypes.Structure):
+        _fields_ = [('dwOSVersionInfoSize', ctypes.c_ulong),
+                    ('dwMajorVersion', ctypes.c_ulong),
+                    ('dwMinorVersion', ctypes.c_ulong),
+                    ('dwBuildNumber', ctypes.c_ulong),
+                    ('dwPlatformId', ctypes.c_ulong),
+                    ('szCSDVersion', ctypes.c_wchar*128),
+                    ('wServicePackMajor', ctypes.c_ushort),
+                    ('wServicePackMinor', ctypes.c_ushort),
+                    ('wSuiteMask', ctypes.c_ushort),
+                    ('wProductType', ctypes.c_byte),
+                    ('wReserved', ctypes.c_byte)]
+
+    os_version = OSVERSIONINFOEXW()
+    os_version.dwOSVersionInfoSize = ctypes.sizeof(os_version)
+    retcode = ctypes.windll.Ntdll.RtlGetVersion(ctypes.byref(os_version))
+    if retcode != 0:
+        raise OSError
+
+    return os_version.dwMajorVersion, os_version.dwMinorVersion, os_version.dwBuildNumber
+
 # get system information
 info = {'os': unknown,
         'processor': unknown,
         'version': unknown,
         'os_version': unknown,
         'bits': unknown,
         'has_sandbox': unknown }
 (system, node, release, version, machine, processor) = platform.uname()
@@ -45,16 +68,24 @@ if system in ["Microsoft", "Windows"]:
     # http://bugs.python.org/issue7860
     if "PROCESSOR_ARCHITEW6432" in os.environ:
         processor = os.environ.get("PROCESSOR_ARCHITEW6432", processor)
     else:
         processor = os.environ.get('PROCESSOR_ARCHITECTURE', processor)
     system = os.environ.get("OS", system).replace('_', ' ')
     (major, minor, _, _, service_pack) = os.sys.getwindowsversion()
     info['service_pack'] = service_pack
+    if major >= 6 and minor >= 2:
+        # On windows >= 8.1 the system call that getwindowsversion uses has
+        # been frozen to always return the same values. In this case we call
+        # the RtlGetVersion API directly, which still provides meaningful
+        # values, at least for now.
+        major, minor, build_number = get_windows_version()
+        version = "%d.%d.%d" % (major, minor, build_number)
+
     os_version = "%d.%d" % (major, minor)
 elif system == "Linux":
     if hasattr(platform, "linux_distribution"):
         (distro, os_version, codename) = platform.linux_distribution()
     else:
         (distro, os_version, codename) = platform.dist()
     if not processor:
         processor = machine