--- a/security/pkix/test/gtest/moz.build
+++ b/security/pkix/test/gtest/moz.build
@@ -32,16 +32,21 @@ LOCAL_INCLUDES += [
     '../../lib',
     '../lib',
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
 
 include('../../warnings.mozbuild')
 
+# GTest uses a variadic macro in a questionable way and it doesn't seem to be
+# possible to selectively disable just that error when -pedantic-errors is set.
+if CONFIG['GNU_CXX'] and not CONFIG['CLANG_CXX']:
+  CXXFLAGS.remove('-pedantic-errors')
+
 # These warnings are disabled in order to minimize the amount of boilerplate
 # required to implement tests, and/or because they originate in the GTest
 # framework in a way we cannot otherwise work around.
 if CONFIG['GNU_CXX']:
   CXXFLAGS += [
     '-Wno-error=shadow',
     '-Wno-old-style-cast',
   ]