diff --git a/compileall.py b/compileall.py
index b2e17001..4ee609c2 100644
--- a/compileall.py
+++ b/compileall.py
@@ -10,10 +10,16 @@ source_dir = sys.argv[2]
 output_dir = sys.argv[3]
 
 def do_compile(src_path, dst_path):
+    assert os.path.isfile(src_path)
+    assert os.path.isfile(dst_path)
     cmd = f'{pkpy_exe} --compile "{src_path}" "{dst_path}"'
     print(src_path)
     assert os.system(cmd) == 0
 
+if os.path.isfile(source_dir):
+    do_compile(source_dir, output_dir)
+    exit(0)
+
 for root, _, files in os.walk(source_dir):
     for file in files:
         if not file.endswith('.py'):