diff --git a/libc/kernel/tools/clean_header.py b/libc/kernel/tools/clean_header.py
index 22e62aa..01569fc 100755
--- a/libc/kernel/tools/clean_header.py
+++ b/libc/kernel/tools/clean_header.py
@@ -62,8 +62,11 @@
         sys.stderr.write( "error: can't parse '%s'" % path )
         sys.exit(1)
 
+    macros = kernel_known_macros.copy()
+    if arch and arch in kernel_default_arch_macros:
+        macros.update(kernel_default_arch_macros[arch])
 
-    blocks.optimizeMacros( kernel_known_macros )
+    blocks.optimizeMacros( macros )
     blocks.optimizeIf01()
     blocks.removeVarsAndFuncs( statics )
     blocks.replaceTokens( kernel_token_replacements )