diff --git a/pyproject.toml b/pyproject.toml
index 6d44c607e..65104ff13 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -72,7 +72,11 @@ typing = ["mypy", "pytest", "types-setuptools", "types-Pillow", "pydicom"]
 zstd = ["pyzstd >= 0.14.3"]
 
 [tool.hatch.build.targets.sdist]
-exclude = [".git_archival.txt"]
+exclude = [
+  ".git_archival.txt",
+  # Submodules with large files; if we don't want them in the repo...
+  "nibabel-data/",
+]
 
 [tool.hatch.build.targets.wheel]
 packages = ["nibabel", "nisext"]