diff --git a/tools/cc.py b/tools/cc.py
index b0e2406..07a8576 100644
--- a/tools/cc.py
+++ b/tools/cc.py
@@ -1186,12 +1186,18 @@ def parse_args():
                         default=sys.stdin, help='input file (default: stdin)')
     parser.add_argument('--output', '-o', type=argparse.FileType('wb'),
                         default=sys.stdout.buffer, help='output file')
+    parser.add_argument('-I', dest='include_dirs', action='append',
+                        default=[], help='include dirs')
     return parser.parse_args()
 
 
-def preprocess(fin):
-    p = subprocess.Popen(CPP, stdin=fin, stdout=subprocess.PIPE)
-    return p.stdout
+def preprocess(fin, include_dirs):
+    cmd = list(CPP) + [f'-I{x}' for x in include_dirs]
+    p = subprocess.Popen(cmd, stdin=fin, stdout=subprocess.PIPE)
+    out, _ = p.communicate()
+    if p.returncode != 0:
+        raise RuntimeError(f'preprocessor error')
+    return io.StringIO(out.decode())
 
 
 def assemble(text, fout):
@@ -1202,7 +1208,7 @@ def assemble(text, fout):
 def main():
     args = parse_args()
 
-    assy = larkparse(preprocess(args.input), debug=args.debug)
+    assy = larkparse(preprocess(args.input, args.include_dirs), debug=args.debug)
     if args.assembly:
         args.output.write(assy.encode() + b'\n')
     else: