diff --git a/core/src/main.py b/core/src/main.py
index 8516f6241..26443e707 100644
--- a/core/src/main.py
+++ b/core/src/main.py
@@ -6,7 +6,13 @@ import storage
 import storage.device
 if __debug__:
     import storage.debug
-from trezor import config, pin, utils  # noqa: F401
+
+import trezor
+import trezor.pin  # noqa: F401
+from trezor import utils
+
+utils.presize_module("trezor", 30)
+utils.presize_module("storage", 12)
 
 if not utils.BITCOIN_ONLY:
     import storage.fido2  # noqa: F401
diff --git a/core/src/trezor/utils.py b/core/src/trezor/utils.py
index 3e835699b..d076975d9 100644
--- a/core/src/trezor/utils.py
+++ b/core/src/trezor/utils.py
@@ -82,6 +82,20 @@ class unimport:
         gc.collect()
 
 
+def presize_module(modname: str, size: int) -> None:
+    """Ensure the module's dict is preallocated to an expected size.
+
+    This is used in modules like `trezor`, whose dict size depends not only on the
+    symbols defined in the file itself, but also on the number of submodules that will
+    be inserted into the module's namespace.
+    """
+    module = sys.modules[modname]
+    for i in range(size):
+        setattr(module, "___PRESIZE_MODULE_%d" % i, None)
+    for i in range(size):
+        delattr(module, "___PRESIZE_MODULE_%d" % i)
+
+
 def ensure(cond: bool, msg: str | None = None) -> None:
     if not cond:
         if msg is None: