diff --git a/bilby_lisa/__init__.py b/bilby_lisa/__init__.py
index ee53be1..acf42a5 100644
--- a/bilby_lisa/__init__.py
+++ b/bilby_lisa/__init__.py
@@ -6,26 +6,3 @@
     from ._version import version as __version__
 except ModuleNotFoundError:  # development mode
     __version__ = "unknown"
-
-import bilby
-import bilby_pipe
-import parallel_bilby
-
-# check the bilby, bilby_pipe and parallel_bilby installations
-error_str = (
-    "`bilby_lisa` currently requires a non-released version of `{}` "
-    "(you have {} installed currently). Please read the README.md file "
-    "in the source repository for full installation instructions"
-)
-if "f027394" not in bilby.__version__:
-    raise ImportError(
-        error_str.format('bilby', bilby.__version__)
-    )
-if "581eb9a" not in bilby_pipe.__version__:
-    raise ImportError(
-        error_str.format('bilby_pipe', bilby_pipe.__version__)
-    )
-if "e4e2f7b" not in parallel_bilby.__version__:
-    raise ImportError(
-        error_str.format('parallel_bilby', parallel_bilby.__version__)
-    )
diff --git a/bilby_lisa/bilby_pipe.py b/bilby_lisa/bilby_pipe.py
index 3318c15..1e84498 100644
--- a/bilby_lisa/bilby_pipe.py
+++ b/bilby_lisa/bilby_pipe.py
@@ -245,6 +245,17 @@ def bilby_pipe_main():
     """A modified, top-level interface for bilby_pipe which first checks the
     `bilby_lisa` installation
     """
-    from .utils import get_version_info
+    from .utils import get_version_info, version_error_string
+    import bilby
+    import bilby_pipe
+
     get_version_info()
+    if "f027394" not in bilby.__version__:
+        raise ImportError(
+            version_error_string.format('bilby', bilby.__version__)
+        )
+    if "581eb9a" not in bilby_pipe.__version__:
+        raise ImportError(
+            version_error_string.format('bilby_pipe', bilby_pipe.__version__)
+        )
     main()
diff --git a/bilby_lisa/parallel_bilby.py b/bilby_lisa/parallel_bilby.py
index 71d8bb5..fee4a0a 100644
--- a/bilby_lisa/parallel_bilby.py
+++ b/bilby_lisa/parallel_bilby.py
@@ -39,6 +39,14 @@ def parallel_bilby_generation_main():
     """A modified, top-level interface for parallel_bilby_generation which
     first checks the `bilby_lisa` installation
     """
-    from .utils import get_version_info
+    from .utils import get_version_info, version_error_string
+    import parallel_bilby
+
     get_version_info()
+    if "e4e2f7b" not in parallel_bilby.__version__:
+        raise ImportError(
+            version_error_string.format(
+                'parallel_bilby', parallel_bilby.__version__
+            )
+        )
     main()
diff --git a/bilby_lisa/utils.py b/bilby_lisa/utils.py
index b645267..bf1881f 100644
--- a/bilby_lisa/utils.py
+++ b/bilby_lisa/utils.py
@@ -3,6 +3,11 @@
 from bilby_pipe.utils import logger
 
 __author__ = ["Charlie Hoy <charlie.hoy@ligo.org>"]
+version_error_string = (
+    "`bilby_lisa` currently requires a non-released version of `{}` "
+    "(you have {} installed currently). Please read the README.md file "
+    "in the source repository for full installation instructions"
+)
 
 
 def get_warning():
diff --git a/pyproject.toml b/pyproject.toml
index b2ea9c0..d8bc7d3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,11 +27,13 @@ requires-python = ">=3.9"
 dependencies = [
 	"bilby",
 	"bilby_pipe",
-	"parallel_bilby"
 ]
 dynamic = ["version"]
 
 [project.optional-dependencies]
+parallel = [
+	"parallel_bilby"
+]
 docs = [
 	"Sphinx >=1.2.2",
 	"sphinx-immaterial",