diff --git a/configure.py b/configure.py
index 5e85ff7..54b7e24 100755
--- a/configure.py
+++ b/configure.py
@@ -44,7 +44,7 @@ parser.add_argument(
     choices=VERSIONS,
     type=str.upper,
     default=VERSIONS[DEFAULT_VERSION],
-    help=f"version to build",
+    help="version to build",
 )
 parser.add_argument(
     "--build-dir",
@@ -70,6 +70,11 @@ parser.add_argument(
     action="store_true",
     help="generate map file(s)",
 )
+parser.add_argument(
+    "--no-asm",
+    action="store_true",
+    help="don't incorporate .s files from asm directory",
+)
 parser.add_argument(
     "--debug",
     action="store_true",
@@ -115,6 +120,8 @@ config.generate_map = args.map
 config.sjiswrap_path = args.sjiswrap
 if not is_windows():
     config.wrapper = args.wrapper
+if args.no_asm:
+    config.asm_dir = None
 
 # Tool versions
 config.binutils_tag = "2.42-1"
diff --git a/tools/project.py b/tools/project.py
index 1160911..0f756cf 100644
--- a/tools/project.py
+++ b/tools/project.py
@@ -54,7 +54,9 @@ class ProjectConfig:
         self.build_dir: Path = Path("build")  # Output build files
         self.src_dir: Path = Path("src")  # C/C++/asm source files
         self.tools_dir: Path = Path("tools")  # Python scripts
-        self.asm_dir: Path = Path("asm")  # Override incomplete objects (for modding)
+        self.asm_dir: Optional[Path] = Path(
+            "asm"
+        )  # Override incomplete objects (for modding)
 
         # Tooling
         self.binutils_tag: Optional[str] = None  # Git tag
@@ -676,6 +678,8 @@ def generate_build_ninja(
                     options[key] = value
 
             unit_src_path = Path(lib.get("src_dir", config.src_dir)) / options["source"]
+
+            unit_asm_path: Optional[Path] = None
             if config.asm_dir is not None:
                 unit_asm_path = (
                     Path(lib.get("asm_dir", config.asm_dir)) / options["source"]
@@ -697,6 +701,7 @@ def generate_build_ninja(
                 link_built_obj = False
 
             # Assembly overrides
+            built_obj_path: Optional[Path] = None
             if unit_asm_path is not None and unit_asm_path.exists():
                 link_built_obj = True
                 built_obj_path = asm_build(obj, options, lib_name, unit_asm_path)