diff --git a/amalgamate.py b/amalgamate.py
index 2f2b51c..710744b 100644
--- a/amalgamate.py
+++ b/amalgamate.py
@@ -7,6 +7,8 @@
 
 import os
 import re
+import sys
+import argparse
 
 SAFETYHOOK_ROOT = Path(__file__).resolve().parent
 PUBLIC_INCLUDE_PATHS = [
@@ -18,6 +20,10 @@
 OUTPUT_DIR = SAFETYHOOK_ROOT / 'amalgamated-dist'
 FILE_HEADER = ['// DO NOT EDIT. This file is auto-generated by `amalgamate.py`.', '']
 
+parser = argparse.ArgumentParser(description='bundles cpp and hpp files together')
+parser.add_argument('--polyfill', action='store_true', 
+        help='replace std::except with a polyfill so it can be compiled on C++20 or older. https://raw.githubusercontent.com/TartanLlama/expected/master/include/tl/expected.hpp')
+
 
 # Python versions before 3.10 don't have the root_dir argument for glob, so we 
 # crudely emulate it here.
@@ -154,8 +160,15 @@ def merge_sources(*, source_dir: Path, covered_headers: Set[Path]):
 
     return output
 
+def do_polyfill(content):
+    return content.replace('#include <expected>', '#if __has_include("expected.hpp")\n#include <expected.hpp>\n#else\n#include <tl/expected.hpp>\n#endif\n') \
+                  .replace('std::expected', 'tl::expected') \
+                  .replace('std::unexpected', 'tl::unexpected')
 
 def main():
+    args = parser.parse_args()
+    polyfill = args.polyfill is True
+
     if OUTPUT_DIR.exists():
         print('Output directory exists. Deleting.')
         rmtree(OUTPUT_DIR)
@@ -164,20 +177,26 @@ def main():
 
     covered_headers = set()
     with open(OUTPUT_DIR / 'safetyhook.hpp', 'w') as f:
-        f.write('\n'.join(FILE_HEADER + merge_headers(
+        content = '\n'.join(FILE_HEADER + merge_headers(
             header='safetyhook.hpp',
             search_paths=PUBLIC_INCLUDE_PATHS,
             covered_headers=covered_headers,
             stack=[],
-        )))
+        ))
+        if polyfill:
+            content = do_polyfill(content)
+        f.write(content)
 
     print(covered_headers)
 
     with open(OUTPUT_DIR / 'safetyhook.cpp', 'w') as f:
-        f.write('\n'.join(FILE_HEADER + merge_sources(
+        content = '\n'.join(FILE_HEADER + merge_sources(
             source_dir=SAFETYHOOK_ROOT / 'src',
             covered_headers=covered_headers,
-        )))
+        ))
+        if polyfill:
+            content = do_polyfill(content)
+        f.write(content)
 
 
 if __name__ == '__main__':