diff --git a/setup.cfg b/setup.cfg
index 400e676..4b9cc3f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,7 +24,7 @@ sections = FUTURE,STDLIB,THIRDPARTY,FIRSTPARTY,LOCALFOLDER
 
 [metadata]
 name = shiv
-version = 1.0.2
+version = 1.0.3
 description = A command line utility for building fully self contained Python zipapps.
 long_description = file: README.md
 long_description_content_type = text/markdown
diff --git a/src/shiv/bootstrap/__init__.py b/src/shiv/bootstrap/__init__.py
index 4542952..6f0c584 100644
--- a/src/shiv/bootstrap/__init__.py
+++ b/src/shiv/bootstrap/__init__.py
@@ -208,6 +208,9 @@ def bootstrap():  # pragma: no cover
     # Find the first instance of an existing site-packages on sys.path
     index = get_first_sitedir_index() or length
 
+    # copy sys.path to determine diff
+    sys_path_before = sys.path.copy()
+
     # append site-packages using the stdlib blessed way of extending path
     # so as to handle .pth files correctly
     site.addsitedir(site_packages)
@@ -215,13 +218,16 @@ def bootstrap():  # pragma: no cover
     # reorder to place our site-packages before any others found
     sys.path = sys.path[:index] + sys.path[length:] + sys.path[index:length]
 
+    # determine newly added paths
+    new_paths = [p for p in sys.path if p not in sys_path_before]
+
     # check if source files have been modified, if required
     if env.no_modify:
         ensure_no_modify(site_packages, env.hashes)
 
-    # add our site-packages to the environment, if requested
+    # add any new paths to the environment, if requested
     if env.extend_pythonpath:
-        extend_python_path(os.environ, sys.path.copy())
+        extend_python_path(os.environ, new_paths)
 
     # if a preamble script was provided, run it
     if env.preamble:
diff --git a/src/shiv/cli.py b/src/shiv/cli.py
index 758e83e..f361091 100644
--- a/src/shiv/cli.py
+++ b/src/shiv/cli.py
@@ -26,7 +26,7 @@
     SOURCE_DATE_EPOCH_ENV,
 )
 
-__version__ = "1.0.2"
+__version__ = "1.0.3"
 
 
 def find_entry_point(site_packages_dirs: List[Path], console_script: str) -> str: