diff --git a/homeassistant/components/diagnostics/util.py b/homeassistant/components/diagnostics/util.py
index d849dc052e4..6441dd9a36f 100644
--- a/homeassistant/components/diagnostics/util.py
+++ b/homeassistant/components/diagnostics/util.py
@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 from collections.abc import Iterable, Mapping
+from copy import deepcopy
 from typing import Any
 
 from homeassistant.core import callback
@@ -10,19 +11,23 @@ from .const import REDACTED
 
 
 @callback
-def async_redact_data(data: Mapping, to_redact: Iterable[Any]) -> dict[str, Any]:
+def async_redact_data(data: Mapping, to_redact: Iterable[Any]) -> Mapping[Any, Any]:
     """Redact sensitive data in a dict."""
     if not isinstance(data, (Mapping, list)):
         return data
 
-    redacted = {**data}
+    redacted = deepcopy(data)
 
-    for key, value in redacted.items():
-        if key in to_redact:
-            redacted[key] = REDACTED
-        elif isinstance(value, dict):
-            redacted[key] = async_redact_data(value, to_redact)
-        elif isinstance(value, list):
-            redacted[key] = [async_redact_data(item, to_redact) for item in value]
+    if isinstance(redacted, dict):
+        for key, value in redacted.items():
+            if key in to_redact:
+                redacted[key] = REDACTED
+            elif isinstance(value, dict):
+                redacted[key] = async_redact_data(value, to_redact)
+            elif isinstance(value, list):
+                redacted[key] = [async_redact_data(item, to_redact) for item in value]
+    elif isinstance(redacted, list):
+        for idx, value in enumerate(redacted):
+            redacted[idx] = async_redact_data(value, to_redact)
 
     return redacted