diff --git a/morgan/__init__.py b/morgan/__init__.py
index 7ff12cb..6872546 100644
--- a/morgan/__init__.py
+++ b/morgan/__init__.py
@@ -20,7 +20,7 @@
 
 from morgan import configurator, metadata, server
 from morgan.__about__ import __version__
-from morgan.utils import Cache, to_single_dash, touch_file
+from morgan.utils import Cache, ListExtendingOrderedDict, to_single_dash, touch_file
 
 PYPI_ADDRESS = "https://pypi.org/simple/"
 PREFERRED_HASH_ALG = "sha256"
@@ -44,9 +44,11 @@ def __init__(self, args: argparse.Namespace):
         self.index_path = args.index_path
         self.index_url = args.index_url
         self.mirror_all_versions: bool = args.mirror_all_versions
-        self.package_type_regex: str = args.package_type_regex
-        self.config = configparser.ConfigParser()
+        self.config = configparser.ConfigParser(
+            strict=False, dict_type=ListExtendingOrderedDict
+        )
         self.config.read(args.config)
+        self.package_type_regex: str = args.package_type_regex
         self.envs = {}
         self._supported_pyversions = []
         self._supported_platforms = []
diff --git a/morgan/utils.py b/morgan/utils.py
index b33048d..af9c9c2 100644
--- a/morgan/utils.py
+++ b/morgan/utils.py
@@ -1,5 +1,6 @@
 import os
 import re
+from collections import OrderedDict
 
 import dateutil  # type: ignore[import-untyped]
 from packaging.requirements import Requirement
@@ -46,6 +47,42 @@ def is_simple_case(self, req):
         return False
 
 
+class ListExtendingOrderedDict(OrderedDict):
+    """An OrderedDict subclass that aggregates list values for duplicate keys.
+
+    This class extends OrderedDict to provide special handling for list values.
+    When a list value is assigned to an existing key, the new list is extended
+    onto the existing list instead of replacing it.
+
+    In the context of configparser, this allows for accumulating multiple values
+    from different sections or repeated keys, such as in multiline requirements.
+
+    Examples:
+        >>> d = MultiOrderedDict()
+        >>> d['key'] = [1, 2]
+        >>> d['key'] = [3, 4]
+        >>> d['key']
+        [1, 2, 3, 4]
+        >>> d['other'] = 'value'
+        >>> d['other'] = 'new_value'  # Non-list values behave normally
+        >>> d['other']
+        'new_value'
+    """
+
+    def __setitem__(self, key, value):
+        """Sets the value for the given key, extending lists if the key exists.
+
+        Args:
+            key: The dictionary key.
+            value: The value to set. If this is a list and the key already exists,
+                the list will be extended to the existing value instead of replacing it.
+        """
+        if isinstance(value, list) and key in self:
+            self[key].extend(value)
+        else:
+            super().__setitem__(key, value)
+
+
 def touch_file(path: str, fileinfo: dict):
     'upload-time: 2025-05-28T18:46:29.349478Z'
     time_str = fileinfo.get('upload-time')