diff --git a/README.rst b/README.rst
index 31aed16..6feb7e2 100644
--- a/README.rst
+++ b/README.rst
@@ -55,21 +55,22 @@ Using bsonjs with pymongo to insert a RawBSONDocument.
 Speed
 =====
 
-bsonjs is roughly 10-15x faster than PyMongo's json_util at decoding BSON to
+bsonjs is roughly 3-4x faster than PyMongo's json_util at decoding BSON to
 JSON and encoding JSON to BSON. See `benchmark.py`::
 
     $ python benchmark.py
     Timing: bsonjs.dumps(b)
-    10000 loops, best of 3: 0.110911846161
-    Timing: json_util.dumps(bson.BSON(b).decode())
-    10000 loops, best of 3: 1.46571397781
-    bsonjs is 13.22x faster than json_util
+    10000 loops, best of 3: 0.04682216700166464
+    Timing: json_util.dumps(bson.decode(b))
+    10000 loops, best of 3: 0.17319270805455744
+    bsonjs is 3.70x faster than json_util
 
     Timing: bsonjs.loads(j)
-    10000 loops, best of 3: 0.0628039836884
-    Timing: bson.BSON().encode(json_util.loads(j))
-    10000 loops, best of 3: 0.683200120926
-    bsonjs is 11.72x faster than json_util
+    10000 loops, best of 3: 0.053156834095716476
+    Timing: bson.encode(json_util.loads(j))
+    10000 loops, best of 3: 0.15982166700996459
+    bsonjs is 3.01x faster than json_util
+
 
 Limitations
 ===========
diff --git a/benchmark.py b/benchmark.py
index ec19635..7d8e96b 100755
--- a/benchmark.py
+++ b/benchmark.py
@@ -53,17 +53,17 @@ def main(iterations):
              "    'date': datetime.datetime(2009, 12, 9, 15),\n"
              "    'regex': bson.Regex('.*', 'i'),\n"
              "}\n"
-             "b = bson.BSON.encode(doc)\n"
+             "b = bson.encode(doc)\n"
              "j = bsonjs.dumps(b)\n")
 
     # dumps
     compare("bsonjs.dumps(b)",
-            "json_util.dumps(bson.BSON(b).decode())",
+            "json_util.dumps(bson.decode(b))",
             iterations,
             setup)
     # loads
     compare("bsonjs.loads(j)",
-            "bson.BSON().encode(json_util.loads(j))",
+            "bson.encode(json_util.loads(j))",
             iterations,
             setup)
 
diff --git a/build-wheels.sh b/build-wheels.sh
index 1015eff..e5d1e02 100755
--- a/build-wheels.sh
+++ b/build-wheels.sh
@@ -43,7 +43,7 @@ for PYBIN in /opt/python/*/bin; do
     fi
     "${PYBIN}/pip" install python-bsonjs --no-index -f dist
     # The tests require PyMongo.
-    "${PYBIN}/pip" install 'pymongo>=3.4'
+    "${PYBIN}/pip" install 'pymongo>=4'
     for TEST_FILE in "${BSONJS_SOURCE_DIRECTORY}"/test/test_*.py; do
         "${PYBIN}/python" "$TEST_FILE" -v
     done
diff --git a/test/test_bsonjs.py b/test/test_bsonjs.py
index 965c403..a64e961 100644
--- a/test/test_bsonjs.py
+++ b/test/test_bsonjs.py
@@ -46,14 +46,14 @@
 
 def to_object(bson_bytes):
     """Return deserialized object from BSON bytes"""
-    return bson.BSON(bson_bytes).decode(CodecOptions(document_class=SON,
-                                                     tz_aware=True,
-                                                     uuid_representation=UuidRepresentation.PYTHON_LEGACY))
+    return bson.decode(bson_bytes, CodecOptions(document_class=SON,
+                                                tz_aware=True,
+                                                uuid_representation=UuidRepresentation.PYTHON_LEGACY))
 
 
 def to_bson(obj):
     """Return serialized BSON string from object"""
-    return bson.BSON.encode(obj, codec_options=CodecOptions(
+    return bson.encode(obj, codec_options=CodecOptions(
         uuid_representation=UuidRepresentation.PYTHON_LEGACY))