diff --git a/mypy.ini b/mypy.ini
index 789ec02eb..b0ed54888 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -132,8 +132,8 @@ disallow_incomplete_defs = True
 [mypy-qutebrowser.commands.*]
 check_untyped_defs = True
 
-# [mypy-qutebrowser.completion.*]
-# check_untyped_defs = True
+[mypy-qutebrowser.completion.*]
+check_untyped_defs = True
 
 [mypy-qutebrowser.javascript.*]
 check_untyped_defs = True
diff --git a/qutebrowser/completion/models/completionmodel.py b/qutebrowser/completion/models/completionmodel.py
index d7cef71e2..9c1e15539 100644
--- a/qutebrowser/completion/models/completionmodel.py
+++ b/qutebrowser/completion/models/completionmodel.py
@@ -19,6 +19,8 @@
 
 """A model that proxies access to one or more completion categories."""
 
+import typing
+
 from PyQt5.QtCore import Qt, QModelIndex, QAbstractItemModel
 
 from qutebrowser.utils import log, qtutils
@@ -41,7 +43,7 @@ class CompletionModel(QAbstractItemModel):
     def __init__(self, *, column_widths=(30, 70, 0), parent=None):
         super().__init__(parent)
         self.column_widths = column_widths
-        self._categories = []
+        self._categories = []  # type: typing.Sequence[QAbstractItemModel]
 
     def _cat_from_idx(self, index):
         """Return the category pointed to by the given index.
diff --git a/qutebrowser/completion/models/listcategory.py b/qutebrowser/completion/models/listcategory.py
index fa58f16b0..2aa71c635 100644
--- a/qutebrowser/completion/models/listcategory.py
+++ b/qutebrowser/completion/models/listcategory.py
@@ -30,13 +30,18 @@ from qutebrowser.completion.models import util
 from qutebrowser.utils import qtutils, log
 
 
+_ItemType = typing.Union[typing.Tuple[str],
+                         typing.Tuple[str, str],
+                         typing.Tuple[str, str, str]]
+
+
 class ListCategory(QSortFilterProxyModel):
 
     """Expose a list of items as a category for the CompletionModel."""
 
     def __init__(self,
                  name: str,
-                 items: typing.Sequence[str],
+                 items: typing.Iterable[_ItemType],
                  sort: bool = True,
                  delete_func: util.DeleteFuncType = None,
                  parent: QWidget = None):
diff --git a/qutebrowser/completion/models/miscmodels.py b/qutebrowser/completion/models/miscmodels.py
index 9cfe22656..a6d2b3b32 100644
--- a/qutebrowser/completion/models/miscmodels.py
+++ b/qutebrowser/completion/models/miscmodels.py
@@ -51,7 +51,7 @@ def helptopic(*, info):
 
 def quickmark(*, info=None):  # pylint: disable=unused-argument
     """A CompletionModel filled with all quickmarks."""
-    def delete(data: typing.Sequence[int]) -> None:
+    def delete(data: typing.Sequence[str]) -> None:
         """Delete a quickmark from the completion menu."""
         name = data[0]
         quickmark_manager = objreg.get('quickmark-manager')
@@ -68,7 +68,7 @@ def quickmark(*, info=None):  # pylint: disable=unused-argument
 
 def bookmark(*, info=None):  # pylint: disable=unused-argument
     """A CompletionModel filled with all bookmarks."""
-    def delete(data: typing.Sequence[int]) -> None:
+    def delete(data: typing.Sequence[str]) -> None:
         """Delete a bookmark from the completion menu."""
         urlstr = data[0]
         log.completion.debug('Deleting bookmark {}'.format(urlstr))
@@ -88,10 +88,10 @@ def session(*, info=None):  # pylint: disable=unused-argument
     from qutebrowser.misc import sessions
     model = completionmodel.CompletionModel()
     try:
-        sessions = ((name,) for name
-                    in sessions.session_manager.list_sessions()
-                    if not name.startswith('_'))
-        model.add_category(listcategory.ListCategory("Sessions", sessions))
+        sess = ((name,) for name
+                in sessions.session_manager.list_sessions()
+                if not name.startswith('_'))
+        model.add_category(listcategory.ListCategory("Sessions", sess))
     except OSError:
         log.completion.exception("Failed to list sessions!")
     return model