diff --git a/b2sdk/_internal/raw_api.py b/b2sdk/_internal/raw_api.py
index 0fe2d84dd..93446c92a 100644
--- a/b2sdk/_internal/raw_api.py
+++ b/b2sdk/_internal/raw_api.py
@@ -553,7 +553,7 @@ def _post_json(self, base_url: str, endpoint: str, auth: str, **params) -> JSON:
         :param args: the rest of the parameters are passed to b2
         :return: the decoded JSON response
         """
-        url = f'{base_url}/b2api/{API_VERSION}/{endpoint}'
+        url = f'{base_url}/b2api/{self.API_VERSION}/{endpoint}'
         headers = {'Authorization': auth}
         return self.b2_http.post_json_return_json(url, headers, params)
 
diff --git a/b2sdk/v2/api.py b/b2sdk/v2/api.py
index afd3ecc0d..8044e667e 100644
--- a/b2sdk/v2/api.py
+++ b/b2sdk/v2/api.py
@@ -25,6 +25,8 @@
 from .file_version import FileVersionFactory
 from .large_file import LargeFileServices
 from .application_key import FullApplicationKey, ApplicationKey, BaseApplicationKey
+from .account_info import AbstractAccountInfo
+from .api_config import DEFAULT_HTTP_API_CONFIG, B2HttpApiConfig
 
 
 class Services(v3.Services):
@@ -48,10 +50,29 @@ class B2Api(v3.B2Api):
     API_VERSION = RAW_API_VERSION
 
     # Legacy init in case something depends on max_workers defaults = 10
-    def __init__(self, *args, **kwargs):
-        kwargs.setdefault('max_upload_workers', 10)
-        kwargs.setdefault('max_copy_workers', 10)
-        super().__init__(*args, **kwargs)
+    def __init__(
+        self,
+        account_info: AbstractAccountInfo | None = None,
+        cache: v3.AbstractCache | None = None,
+        max_upload_workers: int | None = 10,
+        max_copy_workers: int | None = 10,
+        api_config: B2HttpApiConfig = DEFAULT_HTTP_API_CONFIG,
+        max_download_workers: int | None = None,
+        save_to_buffer_size: int | None = None,
+        check_download_hash: bool = True,
+        max_download_streams_per_file: int | None = None,
+    ):
+        super().__init__(
+            account_info=account_info,
+            cache=cache,
+            max_upload_workers=max_upload_workers,
+            max_copy_workers=max_copy_workers,
+            api_config=api_config,
+            max_download_workers=max_download_workers,
+            save_to_buffer_size=save_to_buffer_size,
+            check_download_hash=check_download_hash,
+            max_download_streams_per_file=max_download_streams_per_file,
+        )
 
     def get_bucket_by_id(self, bucket_id: str) -> v3.Bucket:
         try:
diff --git a/b2sdk/v2/api_config.py b/b2sdk/v2/api_config.py
new file mode 100644
index 000000000..7773b2ae8
--- /dev/null
+++ b/b2sdk/v2/api_config.py
@@ -0,0 +1,18 @@
+######################################################################
+#
+# File: b2sdk/v2/api_config.py
+#
+# Copyright 2025 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+from b2sdk import v3
+from .raw_api import B2RawHTTPApi
+
+
+class B2HttpApiConfig(v3.B2HttpApiConfig):
+    DEFAULT_RAW_API_CLASS = B2RawHTTPApi
+
+
+DEFAULT_HTTP_API_CONFIG = B2HttpApiConfig()
diff --git a/b2sdk/v2/session.py b/b2sdk/v2/session.py
index a6ce6d6e9..61f09039a 100644
--- a/b2sdk/v2/session.py
+++ b/b2sdk/v2/session.py
@@ -12,14 +12,16 @@
 from b2sdk import v3
 from .b2http import B2Http
 
+from .account_info import SqliteAccountInfo
 from ._compat import _file_infos_rename
-from .._internal import api_config as _api_config
+from . import api_config as _api_config
 from .._internal import cache as _cache
 from .._internal.account_info import abstract as _abstract
 
 
 # Override to use legacy B2Http
 class B2Session(v3.B2Session):
+    SQLITE_ACCOUNT_INFO_CLASS = staticmethod(SqliteAccountInfo)
     B2HTTP_CLASS = staticmethod(B2Http)
 
     def __init__(
@@ -31,6 +33,7 @@ def __init__(
         if account_info is not None and cache is None:
             # preserve legacy behavior https://github.com/Backblaze/b2-sdk-python/issues/497#issuecomment-2147461352
             cache = _cache.DummyCache()
+
         super().__init__(account_info, cache, api_config)
 
     def create_key(
diff --git a/changelog.d/540.fixed.md b/changelog.d/540.fixed.md
new file mode 100644
index 000000000..034cb7e8a
--- /dev/null
+++ b/changelog.d/540.fixed.md
@@ -0,0 +1 @@
+Fix incorrect reliance on v3 abstractions in apiver v2.
\ No newline at end of file
diff --git a/test/unit/v2/test_session.py b/test/unit/v2/test_session.py
index cd5db1cca..003c535ac 100644
--- a/test/unit/v2/test_session.py
+++ b/test/unit/v2/test_session.py
@@ -15,7 +15,7 @@
 from apiver_deps_exception import Unauthorized
 
 from b2sdk import v3
-from b2sdk.v2 import B2Session
+from b2sdk.v2 import B2Http, B2RawHTTPApi, B2Session
 from test.helpers import patch_bind_params
 
 from ..account_info.fixtures import *  # noqa
@@ -74,6 +74,18 @@ def dummy_session():
     return B2Session()
 
 
+def test_session__default_classes_v2():
+    session = B2Session()
+
+    assert isinstance(session.raw_api, B2RawHTTPApi), 'Expected v2.B2RawHTTPApi, got %s' % type(
+        session.raw_api
+    )
+
+    assert isinstance(session.raw_api.b2_http, B2Http), 'Expected v2.B2Http, got %s' % type(
+        session.raw_api.b2_http
+    )
+
+
 def test_session__upload_file__supports_file_infos(dummy_session, file_info):
     """Test v2.B2Session.upload_file support of deprecated file_infos param"""
     with patch_bind_params(v3.B2Session, 'upload_file') as mock_method, pytest.warns(
diff --git a/test/unit/v_all/test_api.py b/test/unit/v_all/test_api.py
index 93c610d24..d40741e31 100644
--- a/test/unit/v_all/test_api.py
+++ b/test/unit/v_all/test_api.py
@@ -14,6 +14,7 @@
 from apiver_deps import (
     B2Api,
     B2HttpApiConfig,
+    B2Session,
     Bucket,
     EncryptionMode,
     EncryptionSetting,
@@ -73,6 +74,8 @@ def test_api_initialization(self, kwargs, _raw_api_class):
 
         self.api = B2Api(self.account_info, self.cache, api_config=api_config, **kwargs)
 
+        assert isinstance(self.api.session, B2Session)  # ensure correct apiver session is used
+
         assert self.api.account_info is self.account_info
         assert self.api.api_config is api_config
         assert self.api.cache is self.cache