diff --git a/project/arch.mk b/project/arch.mk
index 14fb02d..466bf79 100644
--- a/project/arch.mk
+++ b/project/arch.mk
@@ -1,3 +1,6 @@
+# nt32/nt64
+ARCH = nt$(CC_BITS)
+
 src/internal/nolibc/ptyc_compiler.lo: $(PROJECT_DIR)/src/internal/nolibc/$(ARCH)/ptyc_compiler.s host.tag tree.tag
 	$(CC) -c -o $@ $<