diff --git a/tox_poetry_installer/constants.py b/tox_poetry_installer/constants.py
index 3be4fd8..ccfc6f3 100644
--- a/tox_poetry_installer/constants.py
+++ b/tox_poetry_installer/constants.py
@@ -21,3 +21,6 @@ REPORTER_PREFIX: str = f"{__about__.__title__}:"
 
 # Internal list of packages that poetry has deemed unsafe and are excluded from the lockfile
 UNSAFE_PACKAGES: Set[str] = {"distribute", "pip", "setuptools", "wheel"}
+
+# Number of threads to use for installing dependencies by default
+DEFAULT_INSTALL_THREADS: int = 10
diff --git a/tox_poetry_installer/hooks.py b/tox_poetry_installer/hooks.py
index 7c880ee..871c9f6 100644
--- a/tox_poetry_installer/hooks.py
+++ b/tox_poetry_installer/hooks.py
@@ -12,6 +12,7 @@ from tox.config import Parser as ToxParser
 from tox.venv import VirtualEnv as ToxVirtualEnv
 
 from tox_poetry_installer import __about__
+from tox_poetry_installer import constants
 from tox_poetry_installer import exceptions
 from tox_poetry_installer import installer
 from tox_poetry_installer import logger
@@ -31,7 +32,7 @@ def tox_addoption(parser: ToxParser):
         "--require-poetry",
         action="store_true",
         dest="require_poetry",
-        help="Trigger a failure if Poetry is not available to Tox",
+        help="(deprecated) Trigger a failure if Poetry is not available to Tox",
     )
 
     parser.add_argument(
@@ -39,7 +40,15 @@ def tox_addoption(parser: ToxParser):
         type=int,
         dest="parallelize_locked_install",
         default=None,
-        help="Number of worker threads to use for installing dependencies from the Poetry lockfile in parallel",
+        help="(deprecated) Number of worker threads to use for installing dependencies from the Poetry lockfile in parallel",
+    )
+
+    parser.add_argument(
+        "--parallel-install-threads",
+        type=int,
+        dest="parallel_install_threads",
+        default=constants.DEFAULT_INSTALL_THREADS,
+        help="Number of locked dependencies to install simultaneously; set to 0 to disable parallel installation",
     )
 
     parser.add_testenv_attribute(
@@ -82,13 +91,6 @@ def tox_testenv_install_deps(venv: ToxVirtualEnv, action: ToxAction) -> Optional
     :param action: Tox action object
     """
 
-    if venv.envconfig.config.option.require_poetry:
-        logger.warning(
-            "DEPRECATION WARNING: The '--require-poetry' runtime option is deprecated and will be "
-            "removed in version 1.0.0. Please update test environments that require Poetry to "
-            "set the 'require_poetry = true' option in tox.ini"
-        )
-
     try:
         poetry = utilities.check_preconditions(venv, action)
     except exceptions.SkipEnvironment as err:
@@ -158,11 +160,18 @@ def tox_testenv_install_deps(venv: ToxVirtualEnv, action: ToxAction) -> Optional
         raise err
 
     dependencies = dev_deps + env_deps + project_deps
-    log_parallel = (
-        f" (using {venv.envconfig.config.option.parallelize_locked_install} threads)"
-        if venv.envconfig.config.option.parallelize_locked_install
-        else ""
-    )
+    if (
+        venv.envconfig.config.option.parallel_install_threads
+        != constants.DEFAULT_INSTALL_THREADS
+    ):
+        parallel_threads = venv.envconfig.config.option.parallel_install_threads
+    else:
+        parallel_threads = (
+            venv.envconfig.config.option.parallelize_locked_install
+            if venv.envconfig.config.option.parallelize_locked_install is not None
+            else constants.DEFAULT_INSTALL_THREADS
+        )
+    log_parallel = f" (using {parallel_threads} threads)" if parallel_threads else ""
 
     action.setactivity(
         __about__.__title__,
@@ -172,7 +181,7 @@ def tox_testenv_install_deps(venv: ToxVirtualEnv, action: ToxAction) -> Optional
         poetry,
         venv,
         dependencies,
-        venv.envconfig.config.option.parallelize_locked_install,
+        parallel_threads,
     )
 
     return venv.envconfig.require_locked_deps or None
diff --git a/tox_poetry_installer/installer.py b/tox_poetry_installer/installer.py
index 1685ea0..bbde07f 100644
--- a/tox_poetry_installer/installer.py
+++ b/tox_poetry_installer/installer.py
@@ -5,7 +5,6 @@
 import concurrent.futures
 import contextlib
 import typing
-from typing import Optional
 from typing import Sequence
 from typing import Set
 
@@ -23,7 +22,7 @@ def install(
     poetry: "_poetry.Poetry",
     venv: ToxVirtualEnv,
     packages: Sequence[PoetryPackage],
-    parallels: Optional[int] = None,
+    parallels: int = 0,
 ):
     """Install a bunch of packages to a virtualenv
 
@@ -55,7 +54,7 @@ def install(
         enables/disables the usage of the parallel thread pooler depending on the value of
         the ``parallels`` parameter.
         """
-        if parallels:
+        if parallels > 0:
             with concurrent.futures.ThreadPoolExecutor(
                 max_workers=parallels
             ) as executor:
diff --git a/tox_poetry_installer/utilities.py b/tox_poetry_installer/utilities.py
index 6f7ac80..87e1d98 100644
--- a/tox_poetry_installer/utilities.py
+++ b/tox_poetry_installer/utilities.py
@@ -43,6 +43,19 @@ def check_preconditions(venv: ToxVirtualEnv, action: ToxAction) -> "_poetry.Poet
             f"Skipping isolated packaging build env '{action.name}'"
         )
 
+    if venv.envconfig.config.option.require_poetry:
+        logger.warning(
+            "DEPRECATION: The '--require-poetry' runtime option is deprecated and will be "
+            "removed in version 1.0.0. Please update test environments that require Poetry to "
+            "set the 'require_poetry = true' option in tox.ini"
+        )
+
+    if venv.envconfig.config.option.parallelize_locked_install is not None:
+        logger.warning(
+            "DEPRECATION: The '--parallelize-locked-install' option is deprecated and will "
+            "be removed in version 1.0.0. Please use the '--parallel-install-threads' option."
+        )
+
     from tox_poetry_installer import _poetry
 
     try: