diff --git a/mesonbuild/compilers/mixins/clang.py b/mesonbuild/compilers/mixins/clang.py
index 69d29b70f1bc..89eb099c183e 100644
--- a/mesonbuild/compilers/mixins/clang.py
+++ b/mesonbuild/compilers/mixins/clang.py
@@ -90,6 +90,12 @@ def __init__(self, defines: T.Optional[T.Dict[str, str]]):
         # All Clang backends can also do LLVM IR
         self.can_compile_suffixes.add('ll')
 
+    def get_always_args(self) -> T.List[str]:
+        # Force clang to fail in sanity checks if an unknwon warning option is
+        # user
+        myargs: T.List[str] = ['-Werror=unknown-warning-option']
+        return super().get_always_args() + myargs
+
     def get_crt_compile_args(self, crt_val: str) -> T.List[str]:
         if not isinstance(self.linker, VisualStudioLikeLinkerMixin):
             return []
diff --git a/unittests/internaltests.py b/unittests/internaltests.py
index fb0e4a2fd0ad..9f7bfece4433 100644
--- a/unittests/internaltests.py
+++ b/unittests/internaltests.py
@@ -238,6 +238,15 @@ def test_compiler_args_class_visualstudio(self):
         self.assertEqual(a.to_native(copy=True), ['/nologo', '/showIncludes', '/Zc:__cplusplus', '/validate-charset-'])
 
 
+    def test_clang_always_args_contain_werror_unknown_warning(self):
+        env = get_fake_env()
+        linker = linkers.MoldDynamicLinker([], env, MachineChoice.HOST, '-Wl,', [])
+        cc = ClangCCompiler([], [], '14.0.0', MachineChoice.HOST, env, linker=linker)
+
+        always_args = cc.get_always_args()
+        self.assertIn('-Werror=unknown-warning-option', always_args)
+
+
     def test_msvc_unix_args_to_native(self):
         # joined
         self.assertEqual(MSVCCompiler.unix_args_to_native(['-isystemfoo']), ['/Ifoo'])
diff --git a/unittests/linuxliketests.py b/unittests/linuxliketests.py
index a79bd6d767ee..10401e304242 100644
--- a/unittests/linuxliketests.py
+++ b/unittests/linuxliketests.py
@@ -797,8 +797,8 @@ def test_cpp_std_override(self):
         self.assertNotIn('-std=c++98', plain_comp)
         self.assertNotIn('-std=c++11', plain_comp)
         # Now werror
-        self.assertIn('-Werror', plain_comp)
-        self.assertNotIn('-Werror', c98_comp)
+        self.assertIn('-Werror', plain_comp.split())
+        self.assertNotIn('-Werror', c98_comp.split())
 
     def test_run_installed(self):
         if is_cygwin() or is_osx():