diff --git a/HISTORY.md b/HISTORY.md
index 8b02990495..cbf2f5e0a6 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,6 +1,15 @@
 Release History
 ===============
 
+3.5.2 (2024-03-05)
+------------------
+
+**Fixed**
+- ImportError in an attempt to retrieve `ConnectionInfo`.
+
+**Changed**
+- General performance improvements.
+
 3.5.1 (2024-03-04)
 ------------------
 
diff --git a/src/niquests/__version__.py b/src/niquests/__version__.py
index 9d5100c6c7..d0a4e38883 100644
--- a/src/niquests/__version__.py
+++ b/src/niquests/__version__.py
@@ -9,9 +9,9 @@
 __url__: str = "https://niquests.readthedocs.io"
 
 __version__: str
-__version__ = "3.5.1"
+__version__ = "3.5.2"
 
-__build__: int = 0x030501
+__build__: int = 0x030502
 __author__: str = "Kenneth Reitz"
 __author_email__: str = "me@kennethreitz.org"
 __license__: str = "Apache-2.0"
diff --git a/src/niquests/models.py b/src/niquests/models.py
index ec25e261be..a1dd470860 100644
--- a/src/niquests/models.py
+++ b/src/niquests/models.py
@@ -995,7 +995,7 @@ def lazy(self) -> bool:
         Determine if response isn't received and is actually a placeholder.
         Only significant if request was sent through a multiplexed connection.
         """
-        return hasattr(self, "raw") and self.raw is None and hasattr(self, "_promise")
+        return self.raw is None and hasattr(self, "_promise")
 
     def _gather(self) -> None:
         """internals used for lazy responses. Do not try to access this unless you know what you are doing."""
@@ -1012,6 +1012,7 @@ def __getattribute__(self, item):
                 )
             else:
                 self._gather()
+
         return super().__getattribute__(item)
 
     def __enter__(self):
diff --git a/src/niquests/structures.py b/src/niquests/structures.py
index d8147bbb9b..8d5114ceb5 100644
--- a/src/niquests/structures.py
+++ b/src/niquests/structures.py
@@ -9,7 +9,6 @@
 
 import threading
 import typing
-from collections import OrderedDict
 from collections.abc import Mapping, MutableMapping
 
 from .exceptions import InvalidHeader
@@ -18,6 +17,8 @@
 def _ensure_str_or_bytes(
     key: typing.Any, value: typing.Any
 ) -> tuple[bytes | str, bytes | str]:
+    if isinstance(key, (bytes, str)) and isinstance(value, (bytes, str)):
+        return key, value
     if isinstance(
         value,
         (
@@ -25,8 +26,6 @@ def _ensure_str_or_bytes(
             int,
         ),
     ):
-        if isinstance(key, bytes):
-            key = key.decode()
         value = str(value)
     if isinstance(key, (bytes, str)) is False or (
         value is not None and isinstance(value, (bytes, str)) is False
@@ -63,14 +62,13 @@ class CaseInsensitiveDict(MutableMapping):
     """
 
     def __init__(self, data=None, **kwargs) -> None:
-        self._store: MutableMapping[
-            bytes | str, tuple[bytes | str, bytes | str]
-        ] = OrderedDict()
+        self._store: MutableMapping[bytes | str, tuple[bytes | str, bytes | str]] = {}
         if data is None:
             data = {}
         upstream_dict: bool = hasattr(data, "getlist")
         if upstream_dict:
-            data = dict(data)
+            self.update(data, **kwargs)
+            return
         normalized_items = []
         for k, v in data.items() if hasattr(data, "items") else data:
             normalized_items.append(
diff --git a/src/niquests/utils.py b/src/niquests/utils.py
index b8d0df7a5a..c2ab56c726 100644
--- a/src/niquests/utils.py
+++ b/src/niquests/utils.py
@@ -33,8 +33,6 @@
 )
 from netrc import NetrcParseError, netrc
 
-from urllib3 import ConnectionInfo
-
 from ._compat import HAS_LEGACY_URLLIB3
 
 if HAS_LEGACY_URLLIB3 is False:
@@ -50,6 +48,7 @@
         AsyncResolverDescription,
         AsyncManyResolver,
     )
+    from urllib3 import ConnectionInfo
 else:
     from urllib3_future.util import make_headers, parse_url  # type: ignore[assignment]
     from urllib3_future.contrib.resolver import (  # type: ignore[assignment]
@@ -63,6 +62,7 @@
         AsyncResolverDescription,
         AsyncManyResolver,
     )
+    from urllib3_future import ConnectionInfo  # type: ignore[assignment]
 
 from .__version__ import __version__
 from .cookies import cookiejar_from_dict