diff --git a/pandas/_libs/groupby.pyx b/pandas/_libs/groupby.pyx
index 35a6963165194..e7ac3b8442c6d 100644
--- a/pandas/_libs/groupby.pyx
+++ b/pandas/_libs/groupby.pyx
@@ -869,7 +869,9 @@ def group_last(rank_t[:, :] out,
 
     assert min_count == -1, "'min_count' only used in add and prod"
 
-    if not len(values) == len(labels):
+    # TODO(cython 3.0):
+    # Instead of `labels.shape[0]` use `len(labels)`
+    if not len(values) == labels.shape[0]:
         raise AssertionError("len(index) != len(labels)")
 
     nobs = np.zeros((<object>out).shape, dtype=np.int64)
@@ -960,7 +962,9 @@ def group_nth(rank_t[:, :] out,
 
     assert min_count == -1, "'min_count' only used in add and prod"
 
-    if not len(values) == len(labels):
+    # TODO(cython 3.0):
+    # Instead of `labels.shape[0]` use `len(labels)`
+    if not len(values) == labels.shape[0]:
         raise AssertionError("len(index) != len(labels)")
 
     nobs = np.zeros((<object>out).shape, dtype=np.int64)
@@ -1254,7 +1258,9 @@ def group_max(groupby_t[:, :] out,
 
     assert min_count == -1, "'min_count' only used in add and prod"
 
-    if not len(values) == len(labels):
+    # TODO(cython 3.0):
+    # Instead of `labels.shape[0]` use `len(labels)`
+    if not len(values) == labels.shape[0]:
         raise AssertionError("len(index) != len(labels)")
 
     nobs = np.zeros((<object>out).shape, dtype=np.int64)
@@ -1327,7 +1333,9 @@ def group_min(groupby_t[:, :] out,
 
     assert min_count == -1, "'min_count' only used in add and prod"
 
-    if not len(values) == len(labels):
+    # TODO(cython 3.0):
+    # Instead of `labels.shape[0]` use `len(labels)`
+    if not len(values) == labels.shape[0]:
         raise AssertionError("len(index) != len(labels)")
 
     nobs = np.zeros((<object>out).shape, dtype=np.int64)