diff --git a/problemtools/run/source.py b/problemtools/run/source.py
index 514c6cf7..c646c60e 100644
--- a/problemtools/run/source.py
+++ b/problemtools/run/source.py
@@ -58,6 +58,7 @@ def __init__(self, path, language, work_dir=None, include_dir=None):
 
         # Copy all files
         rutil.add_files(path, self.path)
+        self._code_size = sum(os.path.getsize(f) for f in rutil.list_files_recursive(self.path))
         if include_dir is not None:
             include_dir = os.path.join(include_dir, self.language.lang_id)
             if os.path.isdir(include_dir):
@@ -77,7 +78,7 @@ def __init__(self, path, language, work_dir=None, include_dir=None):
         self.binary = os.path.join(self.path, 'run')
 
     def code_size(self) -> int:
-        return sum(os.path.getsize(x) for x in self.src)
+        return self._code_size
 
     def do_compile(self) -> tuple[bool, str | None]:
         """Compile the source code.