diff --git a/litellm/litellm_core_utils/fallback_utils.py b/litellm/litellm_core_utils/fallback_utils.py
index 52eb35663bd..fefc143ef3a 100644
--- a/litellm/litellm_core_utils/fallback_utils.py
+++ b/litellm/litellm_core_utils/fallback_utils.py
@@ -47,8 +47,9 @@ async def async_completion_with_fallbacks(**kwargs):
             completion_kwargs = safe_deep_copy(base_kwargs)
             # Handle dictionary fallback configurations
             if isinstance(fallback, dict):
-                model = fallback.pop("model", original_model)
-                completion_kwargs.update(fallback)
+                fallback_copy = dict(fallback)  # avoid mutating caller's dict
+                model = fallback_copy.pop("model", original_model)
+                completion_kwargs.update(fallback_copy)
             else:
                 model = fallback