--- a/security/pkix/test/gtest/moz.build
+++ b/security/pkix/test/gtest/moz.build
@@ -51,16 +51,17 @@ if CONFIG['GNU_CXX']:
     '-Wno-old-style-cast',
   ]
   if CONFIG['CLANG_CXX']:
     CXXFLAGS += [
       '-Wno-exit-time-destructors',
       '-Wno-global-constructors',
       '-Wno-thread-safety',
       '-Wno-used-but-marked-unused',
+      '-Wno-zero-as-null-pointer-constant',
     ]
 elif CONFIG['_MSC_VER']:
   CXXFLAGS += [
     '-wd4350', # behavior change: 'std::_Wrap_alloc<std::allocator<_Ty>>::...
     '-wd4275', # non dll-interface class used as base for dll-interface class
     '-wd4548', # Expression before comma has no effect
     '-wd4625', # copy constructor could not be generated.
     '-wd4626', # assugment operator could not be generated.