diff --git a/pgidocgen/mergeindex.py b/pgidocgen/mergeindex.py
index 3c3c9454..ab3829b1 100755
--- a/pgidocgen/mergeindex.py
+++ b/pgidocgen/mergeindex.py
@@ -19,32 +19,60 @@
 
 from .util import unescape_parameter
 
+from typing import TypedDict
+
+
+class IndexObject(TypedDict):
+    objnames: dict[str, list[str]]
+    objtypes: dict[str, str]
+    docnames: list[str]
+    filenames: list[str]
+    titles: list[str]
+    objects: dict[str, list[list[int | str]]]
+
+
+class PartialIndexObject(IndexObject, total=False):
+    objnames: dict[str, list[str]]
+    objtypes: dict[str, str]
+    docnames: list[str]
+    filenames: list[str]
+    titles: list[str]
+    objects: dict[str, list[list[int | str]]]
+
+
+class DoneIndexObject(PartialIndexObject, total=False):
+    namespaces: dict[str, PartialIndexObject]
+
 
 class SearchIndexMerger(object):
 
     def __init__(self):
-        self._indices = {}
+        self._indices: dict[str, IndexObject] = {}
 
-    def add_index(self, namespace, index):
+    def add_index(self, namespace: str, index: IndexObject):
         if index is not None:
             assert namespace not in self._indices
             self._indices[namespace] = index
 
-    def load_index(self, namespace, index_path):
+    def load_index(self, namespace: str, index_path: str):
         with io.open(index_path, "r", encoding="utf-8") as h:
             data = h.read()
             mod = js_index.loads(data)
             self.add_index(namespace, mod)
 
-    def merge(self):
+    def merge(self) -> DoneIndexObject:
 
         if not self._indices:
             raise ValueError
 
-        done = {}
-        namespaces = {}
+        done: DoneIndexObject = {
+            # Initialise empty vars to satisfy type checker
+            "objtypes": {},
+            "namespaces": {}
+        }
+        namespaces: dict[str, PartialIndexObject] = {}
 
-        pairs = []
+        pairs: list[tuple[str, list[str]]] = []
         for ns, index in self._indices.items():
             for k, v in index["objnames"].items():
                 pair = (index["objtypes"][k], v)
@@ -62,31 +90,34 @@ def merge(self):
         new_objnames = {}
         new_objtypes = {}
 
-        objtype_indizes = {}
+        objtype_indices = {
+            "gobject:property": 0
+        }
         for i, (type_, name) in enumerate(pairs):
             new_objnames[str(i)] = name
             new_objtypes[str(i)] = type_
-            objtype_indizes[type_] = i
+            objtype_indices[type_] = i
 
         done["objnames"] = new_objnames
         done["objtypes"] = new_objtypes
 
-        def get_obj_index(ns, old_index):
-            old_index = str(old_index)
+        def get_obj_index(ns: str, old_index: int | str) -> int:
+            inner_old_index = str(old_index)
             index = self._indices[ns]
-            value = index["objtypes"][old_index]
+            value = index["objtypes"][inner_old_index]
             for k, v in done["objtypes"].items():
                 if value == v:
                     return int(k)
             assert 0
+            return 0
 
         # OBJECTS
         for ns, index in self._indices.items():
             namespaces[ns] = {}
 
-            new_titles = []
-            new_filenames = []
-            new_docnames = []
+            new_titles: list[str] = []
+            new_filenames: list[str] = []
+            new_docnames: list[str] = []
             for docname, fn, title in zip(index["docnames"],
                                           index["filenames"], index["titles"]):
                 new_filenames.append(fn)
@@ -99,7 +130,7 @@ def get_obj_index(ns, old_index):
             namespaces[ns]["filenames"] = new_filenames
             namespaces[ns]["docnames"] = new_docnames
 
-            new_objects = {}
+            new_objects: dict[str, list[list[int | str]]] = {}
             for k, attributes in index["objects"].items():
                 if "." in k:
                     k = k.split(".", 1)[-1]
@@ -117,33 +148,34 @@ def get_obj_index(ns, old_index):
                     is_signals = True
 
                 if k not in new_objects:
-                    new_objects[k] = {}
+                    new_objects[k] = []
                 new_attributes = new_objects[k]
 
-                for attr, v in attributes.items():
-                    fn_index, objtype_index, prio, shortanchor = v
+                for v in attributes:
+                    fn_index, objtype_index, prio, _, shortanchor = v
+                    attr: str = str(shortanchor)
                     objtype_index = get_obj_index(ns, objtype_index)
                     new_v = [fn_index, objtype_index, prio, shortanchor]
 
                     # Move things around so that signals and properties
                     # better match devhelp output.
                     if is_props:
-                        new_v[1] = objtype_indizes["gobject:property"]
+                        new_v[1] = objtype_indices["gobject:property"]
                         new_v[3] = orig_k + "." + attr
                         attr = "%s:%s" % (
                             orig_k.rsplit(".", 1)[0], unescape_parameter(attr))
                     elif is_signals:
-                        new_v[1] = objtype_indizes["gobject:signal"]
+                        new_v[1] = objtype_indices["gobject:signal"]
                         new_v[3] = orig_k + "." + attr
                         attr = "%s::%s" % (
                             orig_k.rsplit(".", 1)[0], unescape_parameter(attr))
                     elif attr.startswith("do_"):
                         # change vfunc object type
                         # XXX: there could be methods called "do_XXX"..
-                        new_v[1] = objtype_indizes["gobject:vfunc"]
+                        new_v[1] = objtype_indices["gobject:vfunc"]
 
                     assert attr not in new_attributes
-                    new_attributes[attr] = new_v
+                    new_attributes.append([])
 
             namespaces[ns]["objects"] = new_objects
 
@@ -152,7 +184,7 @@ def get_obj_index(ns, old_index):
         return done
 
 
-def mergeindex(path):
+def mergeindex(path: str):
     """Merge searchindex files in subdirectories of `path` and
     create a searchindex files under `path`
     """