diff --git a/mesonbuild/dependencies.py b/mesonbuild/dependencies.py
index ef7be3a5e..ea5660e2a 100644
--- a/mesonbuild/dependencies.py
+++ b/mesonbuild/dependencies.py
@@ -1631,6 +1631,7 @@ class LLVMDependency(Dependency):
     llvmconfig = None
     _llvmconfig_found = False
     __best_found = None
+    __cpp_blacklist = {'-DNDEBUG'}
 
     def __init__(self, environment, kwargs):
         super().__init__('llvm-config', kwargs)
@@ -1676,7 +1677,7 @@ class LLVMDependency(Dependency):
             p, out = Popen_safe([self.llvmconfig, '--cppflags'])[:2]
             if p.returncode != 0:
                 raise DependencyException('Could not generate includedir for LLVM.')
-            self.cargs = shlex.split(out)
+            self.cargs = list(mesonlib.OrderedSet(shlex.split(out)).difference(self.__cpp_blacklist))
 
             p, out = Popen_safe([self.llvmconfig, '--components'])[:2]
             if p.returncode != 0: