diff --git a/IPython/core/completerlib.py b/IPython/core/completerlib.py
index 5e59c6abcdf..2835b19df29 100644
--- a/IPython/core/completerlib.py
+++ b/IPython/core/completerlib.py
@@ -117,7 +117,10 @@ def get_root_modules():
         # Don't try to scan for modules every time.
         return list(sys.builtin_module_names)
 
-    rootmodules_cache = ip.db.get('rootmodules_cache', {})
+    if getattr(ip.db, '_mock', False):
+        rootmodules_cache = {}
+    else:
+        rootmodules_cache = ip.db.get('rootmodules_cache', {})
     rootmodules = list(sys.builtin_module_names)
     start_time = time()
     store = False
diff --git a/IPython/core/interactiveshell.py b/IPython/core/interactiveshell.py
index 0a528c51f20..8cd5308ae74 100644
--- a/IPython/core/interactiveshell.py
+++ b/IPython/core/interactiveshell.py
@@ -42,6 +42,7 @@
 except ModuleNotFoundError:
 
     class PickleShareDB:  # type: ignore [no-redef]
+        _mock = True
         def __init__(self, path):
             pass