diff --git a/spacy/ml/models/coref.py b/spacy/ml/models/coref.py
index d59619498..96fad8019 100644
--- a/spacy/ml/models/coref.py
+++ b/spacy/ml/models/coref.py
@@ -56,6 +56,7 @@ def convert_coref_clusterer_inputs(model: Model, X: List[Floats2d], is_train: bo
     def backprop(args: ArgsKwargs) -> List[Floats2d]:
         # convert to xp and wrap in list
         gradients = torch2xp(args.args[0])
+        assert isinstance(gradients, Floats2d)
         return [gradients]
 
     return ArgsKwargs(args=(word_features,), kwargs={}), backprop
diff --git a/spacy/ml/models/coref_util.py b/spacy/ml/models/coref_util.py
index 8d0ff7bb0..dc9366a61 100644
--- a/spacy/ml/models/coref_util.py
+++ b/spacy/ml/models/coref_util.py
@@ -1,6 +1,6 @@
+from typing import List, Tuple, Set, Dict, cast
 from thinc.types import Ints2d
 from spacy.tokens import Doc
-from typing import List, Tuple, Set
 
 # type alias to make writing this less tedious
 MentionClusters = List[List[Tuple[int, int]]]
@@ -111,9 +111,9 @@ def select_non_crossing_spans(
     Nested spans are allowed.
     """
     # ported from Model._extract_top_spans
-    selected = []
-    start_to_max_end = {}
-    end_to_min_start = {}
+    selected: List[int] = []
+    start_to_max_end: Dict[int, int] = {}
+    end_to_min_start: Dict[int, int] = {}
 
     for idx in idxs:
         if len(selected) >= limit or idx > len(starts):
@@ -188,7 +188,7 @@ def create_gold_scores(
     """
     # make a mapping of mentions to cluster id
     # id is not important but equality will be
-    ment2cid = {}
+    ment2cid: Dict[Tuple[int, int], int] = {}
     for cid, cluster in enumerate(clusters):
         for ment in cluster:
             ment2cid[ment] = cid
@@ -196,7 +196,7 @@ def create_gold_scores(
     ll = len(ments)
     out = []
     # The .tolist() call is necessary with cupy but not numpy
-    mentuples = [tuple(mm.tolist()) for mm in ments]
+    mentuples = [cast(Tuple[int, int], tuple(mm.tolist())) for mm in ments]
     for ii, ment in enumerate(mentuples):
         if ment not in ment2cid:
             # this is not in a cluster so it has no antecedent
diff --git a/spacy/pipeline/coref.py b/spacy/pipeline/coref.py
index 76e790896..ebdb3b9d0 100644
--- a/spacy/pipeline/coref.py
+++ b/spacy/pipeline/coref.py
@@ -259,7 +259,7 @@ class CoreferenceResolver(TrainablePipe):
         span_idxs = create_head_span_idxs(ops, len(example.predicted))
         gscores = create_gold_scores(span_idxs, clusters)
         # TODO fix type here. This is bools but asarray2f wants ints.
-        gscores = ops.asarray2f(gscores)
+        gscores = ops.asarray2f(gscores)  # type: ignore
         # top_gscores = xp.take_along_axis(gscores, cidx, axis=1)
         top_gscores = xp.take_along_axis(gscores, mention_idx, axis=1)
         # now add the placeholder