diff --git a/src/transformers/training_args.py b/src/transformers/training_args.py
index c4577d14f6d89b..e203d6a3ff642b 100644
--- a/src/transformers/training_args.py
+++ b/src/transformers/training_args.py
@@ -175,7 +175,8 @@ class OptimizerNames(ExplicitEnum):
 
 # Sometimes users will pass in a `str` repr of a dict in the CLI
 # We need to track what fields those can be. Each time a new arg
-# has a dict type, it must be added to this list
+# has a dict type, it must be added to this list.
+# Important: These should be typed with Optional[Union[dict,str,...]]
 VALID_DICT_FIELDS = [
     "accelerator_config",
     "fsdp_config",
@@ -1148,7 +1149,7 @@ class TrainingArguments:
             )
         },
     )
-    accelerator_config: Optional[Union[AcceleratorConfig, dict, str]] = field(
+    accelerator_config: Optional[Union[dict, str, AcceleratorConfig]] = field(
         default=None,
         metadata={
             "help": (