diff --git a/.github/workflows/github-actions.yml b/.github/workflows/github-actions.yml
index 66533c13d..d75bdb1a0 100644
--- a/.github/workflows/github-actions.yml
+++ b/.github/workflows/github-actions.yml
@@ -21,6 +21,7 @@ env:
   PYMONGO_3_9: 3.9
   PYMONGO_3_11: 3.11
   PYMONGO_3_12: 3.12
+  PYMONGO_4_0: 4.0
 
   MAIN_PYTHON_VERSION: 3.7
 
@@ -61,6 +62,9 @@ jobs:
           - python-version: 3.7
             MONGODB: $MONGODB_4_4
             PYMONGO: $PYMONGO_3_12
+          - python-version: 3.9
+            MONGODB: $MONGODB_4_4
+            PYMONGO: $PYMONGO_4_0
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}
diff --git a/mongoengine/context_managers.py b/mongoengine/context_managers.py
index 0ca2622c5..eb9c99622 100644
--- a/mongoengine/context_managers.py
+++ b/mongoengine/context_managers.py
@@ -210,13 +210,14 @@ def __init__(self, alias=DEFAULT_CONNECTION_NAME):
         }
 
     def _turn_on_profiling(self):
-        self.initial_profiling_level = self.db.profiling_level()
-        self.db.set_profiling_level(0)
+        profile_update_res = self.db.command({"profile": 0})
+        self.initial_profiling_level = profile_update_res["was"]
+
         self.db.system.profile.drop()
-        self.db.set_profiling_level(2)
+        self.db.command({"profile": 2})
 
     def _resets_profiling(self):
-        self.db.set_profiling_level(self.initial_profiling_level)
+        self.db.command({"profile": self.initial_profiling_level})
 
     def __enter__(self):
         self._turn_on_profiling()
diff --git a/mongoengine/document.py b/mongoengine/document.py
index e56a9e7c2..5d6a47a0e 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -888,10 +888,6 @@ def ensure_indexes(cls):
         index_cls = cls._meta.get("index_cls", True)
 
         collection = cls._get_collection()
-        # 746: when connection is via mongos, the read preference is not necessarily an indication that
-        # this code runs on a secondary
-        if not collection.is_mongos and collection.read_preference > 1:
-            return
 
         # determine if an index which we are creating includes
         # _cls as its first field; if so, we can avoid creating
diff --git a/setup.py b/setup.py
index bb777da0e..78e20331b 100644
--- a/setup.py
+++ b/setup.py
@@ -142,7 +142,7 @@ def run_tests(self):
     platforms=["any"],
     classifiers=CLASSIFIERS,
     python_requires=">=3.6",
-    install_requires=["pymongo>=3.4, <4.0"],
+    install_requires=["pymongo>=3.4,<=4.0"],
     cmdclass={"test": PyTest},
     **extra_opts
 )
diff --git a/tests/test_context_managers.py b/tests/test_context_managers.py
index 4ea7fa5ab..68dc8f4be 100644
--- a/tests/test_context_managers.py
+++ b/tests/test_context_managers.py
@@ -269,17 +269,23 @@ def test_query_counter_temporarily_modifies_profiling_level(self):
         connect("mongoenginetest")
         db = get_db()
 
-        initial_profiling_level = db.profiling_level()
+        def _current_profiling_level():
+            return db.command({"profile": -1})["was"]
+
+        def _set_profiling_level(lvl):
+            db.command({"profile": lvl})
+
+        initial_profiling_level = _current_profiling_level()
 
         try:
             new_level = 1
-            db.set_profiling_level(new_level)
-            assert db.profiling_level() == new_level
+            _set_profiling_level(new_level)
+            assert _current_profiling_level() == new_level
             with query_counter():
-                assert db.profiling_level() == 2
-            assert db.profiling_level() == new_level
+                assert _current_profiling_level() == 2
+            assert _current_profiling_level() == new_level
         except Exception:
-            db.set_profiling_level(
+            _set_profiling_level(
                 initial_profiling_level
             )  # Ensures it gets reseted no matter the outcome of the test
             raise
diff --git a/tox.ini b/tox.ini
index 9925787b2..98c367b44 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,5 +10,6 @@ deps =
     mg39: pymongo>=3.9,<3.10
     mg311: pymongo>=3.11,<3.12
     mg312: pymongo>=3.12,<3.13
+    mg4: pymongo>=4.0,<4.1
 setenv =
     PYTHON_EGG_CACHE = {envdir}/python-eggs