diff --git a/sphinx/domains/c.py b/sphinx/domains/c.py
index a1c96afe59..15e8087df7 100644
--- a/sphinx/domains/c.py
+++ b/sphinx/domains/c.py
@@ -3304,7 +3304,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
 
     return {
         'version': 'builtin',
-        'env_version': 1,
+        'env_version': 2,
         'parallel_read_safe': True,
         'parallel_write_safe': True,
     }