--- a/dom/media/webrtc/moz.build
+++ b/dom/media/webrtc/moz.build
@@ -89,10 +89,11 @@ if CONFIG['GNU_CC'] or CONFIG['CLANG_CL'
 
 FINAL_LIBRARY = 'xul'
 
 if CONFIG['_MSC_VER']:
     CXXFLAGS += [
         '-wd4275', # non dll-interface class used as base for dll-interface class
         '-wd4312', # This is intended as a temporary hack to support building with VS2015
                    # 'reinterpret_cast': conversion from 'DWORD' to 'HANDLE' of greater size
+        '-wd4474', # 'sscanf_s' : too many arguments passed for format string
     ]
     DEFINES['__PRETTY_FUNCTION__'] = '__FUNCSIG__'

--- a/media/webrtc/signaling/test/moz.build
+++ b/media/webrtc/signaling/test/moz.build
@@ -19,8 +19,10 @@ if CONFIG['OS_TARGET'] != 'WINNT' and CO
 include('/ipc/chromium/chromium-config.mozbuild')
 include('common.build')
 
 USE_LIBS += [
     '/media/webrtc/signalingtest/signaling_ecc/ecc',
     'mtransport_s',
 ]
 
+if CONFIG['_MSC_VER']:
+    CXXFLAGS += ['-wd4474']