diff --git a/acbs/ab3cfg.py b/acbs/ab4cfg.py
similarity index 69%
rename from acbs/ab3cfg.py
rename to acbs/ab4cfg.py
index 5983a37..13cd8db 100644
--- a/acbs/ab3cfg.py
+++ b/acbs/ab4cfg.py
@@ -5,9 +5,9 @@
 from pyparsing import ParseException # type: ignore
 
 
-def is_in_stage2_file(ab3cfg_path: str) -> bool:
-    with open(ab3cfg_path) as f:
-        vars = bashvar.eval_bashvar(f.read(), filename=ab3cfg_path)
+def is_in_stage2_file(ab4cfg_path: str) -> bool:
+    with open(ab4cfg_path) as f:
+        vars = bashvar.eval_bashvar(f.read(), filename=ab4cfg_path)
         stage2_val: str = vars.get('ABSTAGE2')
         return stage2_val == '1'
     return False
@@ -21,12 +21,12 @@ def is_in_stage2() -> bool:
     """
     Return whether the current environment is in a stage2 development phase.
     """
-    ab3cfg_path: str = os.path.join(AUTOBUILD_CONF_DIR, 'ab3cfg.sh')
+    ab4cfg_path: str = os.path.join(AUTOBUILD_CONF_DIR, 'ab4cfg.sh')
     try:
-        return is_in_stage2_env() or is_in_stage2_file(ab3cfg_path)
+        return is_in_stage2_env() or is_in_stage2_file(ab4cfg_path)
     except OSError as e:
-        raise RuntimeError(f'Unable to read Autobuild config file {ab3cfg_path}.') from e
+        raise RuntimeError(f'Unable to read Autobuild config file {ab4cfg_path}.') from e
     except ParseException as e:
-        raise RuntimeError(f'Error occurred while parsing Autobuild config file {ab3cfg_path}.') from e
+        raise RuntimeError(f'Error occurred while parsing Autobuild config file {ab4cfg_path}.') from e
     except Exception as e:
         raise RuntimeError(f'Error occurred while checking whether stage 2 mode is enabled.') from e
diff --git a/acbs/main.py b/acbs/main.py
index bf7c6bb..dcc05d8 100644
--- a/acbs/main.py
+++ b/acbs/main.py
@@ -12,7 +12,7 @@
 import acbs.parser
 
 from acbs import __version__
-from acbs.ab3cfg import is_in_stage2
+from acbs.ab4cfg import is_in_stage2
 from acbs.base import ACBSPackageInfo
 from acbs.checkpoint import ACBSShrinkWrap, do_shrink_wrap, checkpoint_to_group
 from acbs.const import CONF_DIR, DUMP_DIR, LOG_DIR, TMP_DIR, AUTOBUILD_CONF_DIR