diff --git a/.gitmodules b/.gitmodules
index 6298a92..1090dee 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,9 +1,9 @@
 [submodule "fastjet"]
-	path = fastjet-core
+	path = extern/fastjet-core
 	url = https://gitlab.com/fastjet/fastjet.git
 [submodule "pybind11"]
 	path = pybind11
 	url = https://github.com/pybind/pybind11.git
 [submodule "fastjet-contrib"]
-	path = fastjet-contrib
+	path = extern/fastjet-contrib
 	url = https://github.com/cms-externals/fastjet-contrib.git
diff --git a/MANIFEST.in b/MANIFEST.in
index 7796d52..9cefe04 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,7 +1,6 @@
 graft src
 graft tests
-graft fastjet-core
-graft fastjet-contrib
+graft extern
 graft pybind11
 global-exclude .git .gitmodules
 include LICENSE README.md pyproject.toml setup.py setup.cfg patch_clustersequence.txt
diff --git a/fastjet-contrib b/extern/fastjet-contrib
similarity index 100%
rename from fastjet-contrib
rename to extern/fastjet-contrib
diff --git a/fastjet-core b/extern/fastjet-core
similarity index 100%
rename from fastjet-core
rename to extern/fastjet-core
diff --git a/setup.py b/setup.py
index e90bcf3..5697138 100644
--- a/setup.py
+++ b/setup.py
@@ -24,9 +24,9 @@
 CGAL_ZIP = "https://github.com/CGAL/cgal/releases/download/v5.6/CGAL-5.6-library.zip"
 
 DIR = pathlib.Path(__file__).parent.resolve()
-FASTJET = DIR / "fastjet-core"
-FASTJET_CONTRIB = DIR / "fastjet-contrib"
-PYTHON = DIR / "src/fastjet"
+FASTJET = DIR / "extern" / "fastjet-core"
+FASTJET_CONTRIB = DIR / "extern" / "fastjet-contrib"
+PYTHON = DIR / "src" / "fastjet"
 OUTPUT = PYTHON / "_fastjet_core"