diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 50965891..a2a57b2c 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -15,6 +15,13 @@ paths are considered internals and can change in minor and patch releases.
 v4.45.0 (unreleased)
 --------------------
 
+Fixed
+^^^^^
+- Overrides for nested keys in dict. Issue (`#823
+  <https://github.com/omni-us/jsonargparse/issues/823>`__).
+- ``Issue-823`` (`#824
+  <https://github.com/omni-us/jsonargparse/pull/824>`__).
+
 Added
 ^^^^^
 - Signature methods now when given ``sub_configs=True``, list of paths types can
diff --git a/jsonargparse/_typehints.py b/jsonargparse/_typehints.py
index a7fa7fea..910ed000 100644
--- a/jsonargparse/_typehints.py
+++ b/jsonargparse/_typehints.py
@@ -919,7 +919,11 @@ def adapt_typehints(
     elif typehint_origin in mapping_origin_types:
         if isinstance(val, NestedArg):
             if isinstance(prev_val, dict):
-                val = {**prev_val, val.key: val.val}
+                if isinstance(val.key, str) and "." in val.key:
+                    key_prefix, key_suffix = val.key.split(".", 1)
+                    val = {**prev_val, key_prefix: {key_suffix: val.val}}
+                else:
+                    val = {**prev_val, val.key: val.val}
             else:
                 val = {val.key: val.val}
         elif isinstance(val, MappingProxyType):