diff --git a/HISTORY.rst b/HISTORY.rst
index ffaf498..c5009c1 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -2,6 +2,10 @@
 History
 =======
 
+1.2.2 (2024-08-29)
+------------------
+* Fix wheel builds
+
 1.2.1 (2024-08-05)
 ------------------
 
diff --git a/MANIFEST.in b/MANIFEST.in
index eadbe6f..5dc7bd7 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,4 +1,2 @@
-include *.rst
-include Makefile
-recursive-include examples *.ipynb
-recursive-include src *.h
+exclude examples/*
+include src/_mt2/*.h
diff --git a/Makefile b/Makefile
index 0399c58..1073b90 100644
--- a/Makefile
+++ b/Makefile
@@ -8,10 +8,13 @@ clean: clean-build clean-pyc clean-venv
 .PHONY: clean-build
 clean-build:
 	rm -rf build/
+	rm -rf testdir/
 	rm -rf dist/
 	rm -rf .eggs/
+	rm -rf src/*.egg-info/
 	find . -name '*.egg-info' -delete
 	find . -name '*.egg' -delete
+	find . -name '*.so' -delete
 
 .PHONY: clean-pyc
 clean-pyc:
@@ -27,3 +30,21 @@ clean-venv:
 .PHONY: test
 test: install
 	uv run --locked python -m unittest discover tests
+
+.PHONY: build
+build: install
+	@# Slightly disgusting; just installing the `build` module into the working venv and
+	@# removing after we're done.
+	uv pip install build
+	uv run python -m build
+	uv pip uninstall build
+
+.PHONY: test_wheel
+test_wheel: clean build
+	@# Build the wheel, then install it and check that we can import it.
+	rm -rf testdir && mkdir testdir
+	cd testdir && uv venv
+	cd testdir && uv pip install `find ../dist/ -name *.whl`
+	testdir/.venv/bin/python -c "from mt2 import mt2"
+	rm -r testdir
+
diff --git a/pyproject.toml b/pyproject.toml
index ced8b60..ca1f2b3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "mt2"
-version = "1.2.1"
+version = "1.2.2"
 description = "Stransverse mass computation as a numpy ufunc."
 authors = [
     { name = "Tom Gillam", email = "tpgillam@googlemail.com" },
@@ -29,8 +29,3 @@ urls = { Homepage = "https://github.com/tpgillam/mt2" }
 requires = ["setuptools>=61.0", "numpy"]
 build-backend = "setuptools.build_meta"
 
-[tool.setuptools.packages.find]
-include = ["mt2*"]
-
-[tool.setuptools.package-data]
-mt2 = ["src/*.h", "src/*.cpp"]
diff --git a/setup.py b/setup.py
index 63cf8eb..5c537e8 100644
--- a/setup.py
+++ b/setup.py
@@ -2,13 +2,13 @@
 
 import numpy
 
-__version__ = "1.2.1"
+__version__ = "1.2.2"
 
 setup(
     ext_modules=[
         Extension(
-            "_mt2",
-            ["src/main.cpp"],
+            "mt2._mt2",
+            ["src/_mt2/main.cpp"],
             define_macros=[
                 # Pass in the version info so we can expose it in the extension.
                 ("VERSION_INFO", __version__),
@@ -19,7 +19,7 @@
                 # citation information elsewhere.
                 ("DISABLE_COPYRIGHT_PRINTING", "1"),
             ],
-            include_dirs=[numpy.get_include(), "src"],
+            include_dirs=[numpy.get_include()],
             language="c++",
             extra_compile_args=["-std=c++11"],
         ),
diff --git a/src/lester_mt2_bisect_v7.h b/src/_mt2/lester_mt2_bisect_v7.h
similarity index 100%
rename from src/lester_mt2_bisect_v7.h
rename to src/_mt2/lester_mt2_bisect_v7.h
diff --git a/src/main.cpp b/src/_mt2/main.cpp
similarity index 100%
rename from src/main.cpp
rename to src/_mt2/main.cpp
diff --git a/src/mt2_Lallyver2.h b/src/_mt2/mt2_Lallyver2.h
similarity index 100%
rename from src/mt2_Lallyver2.h
rename to src/_mt2/mt2_Lallyver2.h
diff --git a/src/mt2_bisect.h b/src/_mt2/mt2_bisect.h
similarity index 100%
rename from src/mt2_bisect.h
rename to src/_mt2/mt2_bisect.h
diff --git a/mt2/__init__.py b/src/mt2/__init__.py
similarity index 97%
rename from mt2/__init__.py
rename to src/mt2/__init__.py
index 026b10f..77e6114 100644
--- a/mt2/__init__.py
+++ b/src/mt2/__init__.py
@@ -2,9 +2,9 @@
 
 import numpy
 
-from _mt2 import mt2_lester_ufunc, mt2_tombs_ufunc  # pyright: ignore [reportMissingImports]
+from mt2._mt2 import mt2_lester_ufunc, mt2_tombs_ufunc  # pyright: ignore [reportMissingImports]
 
-__version__ = "1.2.1"
+__version__ = "1.2.2"
 
 __all__ = ["mt2", "mt2_arxiv", "mt2_ufunc"]
 
diff --git a/mt2/diagnostics.py b/src/mt2/diagnostics.py
similarity index 100%
rename from mt2/diagnostics.py
rename to src/mt2/diagnostics.py
diff --git a/tests/common.py b/tests/common.py
index 31f5456..49fb4b2 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -1,4 +1,4 @@
-from _mt2 import mt2_lally_ufunc, mt2_lester_ufunc, mt2_tombs_ufunc
+from mt2._mt2 import mt2_lally_ufunc, mt2_lester_ufunc, mt2_tombs_ufunc
 
 
 def mt2_lally(*args, desired_precision_on_mt2=0.0, out=None):