--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -227,17 +227,17 @@ def get_compiler_info(compiler, language
         %COMPILER clang-cl
         %VERSION _MSC_FULL_VER
         #else
         %COMPILER msvc
         %VERSION _MSC_FULL_VER
         #endif
         #elif defined(__clang__)
         %COMPILER clang
-        #  if !__cplusplus || __cpp_static_assert
+        #  if !__cplusplus || __has_feature(cxx_alignof)
         %VERSION __clang_major__.__clang_minor__.__clang_patchlevel__
         #  endif
         #elif defined(__GNUC__)
         %COMPILER gcc
         %VERSION __GNUC__.__GNUC_MINOR__.__GNUC_PATCHLEVEL__
         #endif
 
         #if __cplusplus

--- a/python/mozbuild/mozbuild/test/configure/test_toolchain_configure.py
+++ b/python/mozbuild/mozbuild/test/configure/test_toolchain_configure.py
@@ -97,17 +97,17 @@ def CLANGXX(version):
             SUPPORTS_GNUXX11)
 
 
 CLANG_3_3 = CLANG('3.3.0') + DEFAULT_C99
 CLANGXX_3_3 = CLANGXX('3.3.0')
 CLANG_3_6 = CLANG('3.6.2') + DEFAULT_C11
 CLANGXX_3_6 = CLANGXX('3.6.2') + {
     '-std=gnu++11': {
-        '__cpp_static_assert': '200410',
+        '__has_feature(cxx_alignof)': '1',
     },
 }
 
 
 @memoize
 def VS(version):
     version = Version(version)
     return FakeCompiler({

--- a/python/mozbuild/mozbuild/test/configure/test_toolchain_helpers.py
+++ b/python/mozbuild/mozbuild/test/configure/test_toolchain_helpers.py
@@ -21,37 +21,44 @@ from mozunit import (
 from mozbuild.preprocessor import Preprocessor
 from mozbuild.util import ReadOnlyNamespace
 from mozpack import path as mozpath
 
 
 class CompilerPreprocessor(Preprocessor):
     VARSUBST = re.compile('(?P<VAR>\w+)', re.U)
     NON_WHITESPACE = re.compile('\S')
+    HAS_FEATURE = re.compile('(__has_feature)\(([^\)]*)\)')
 
     def __init__(self, *args, **kwargs):
         Preprocessor.__init__(self, *args, **kwargs)
         self.do_filter('c_substitution')
         self.setMarker('#\s*')
 
-    def do_if(self, *args, **kwargs):
+    def do_if(self, expression, **kwargs):
         # The C preprocessor handles numbers following C rules, which is a
         # different handling than what our Preprocessor does out of the box.
         # Hack around it enough that the configure tests work properly.
         context = self.context
         def normalize_numbers(value):
             if isinstance(value, types.StringTypes):
                 if value[-1:] == 'L' and value[:-1].isdigit():
                     value = int(value[:-1])
             return value
+        # Our Preprocessor doesn't handle macros with parameters, so we hack
+        # around that for __has_feature()-like things.
+        def normalize_has_feature(expr):
+            return self.HAS_FEATURE.sub(r'\1\2', expr)
         self.context = self.Context(
-            (k, normalize_numbers(v)) for k, v in context.iteritems()
+            (normalize_has_feature(k), normalize_numbers(v))
+            for k, v in context.iteritems()
         )
         try:
-            return Preprocessor.do_if(self, *args, **kwargs)
+            return Preprocessor.do_if(self, normalize_has_feature(expression),
+                                      **kwargs)
         finally:
             self.context = context
 
     class Context(dict):
         def __missing__(self, key):
             return None
 
     def filter_c_substitution(self, line):