diff --git a/src/diffraxtra/__init__.py b/src/diffraxtra/__init__.py
index 1644568..9391555 100644
--- a/src/diffraxtra/__init__.py
+++ b/src/diffraxtra/__init__.py
@@ -6,9 +6,12 @@
     "VectorizedDenseInterpolation",
 ]
 
+from ._src import (
+    AbstractVectorizedDenseInterpolation,
+    DiffEqSolver,
+    VectorizedDenseInterpolation,
+)
 from ._version import (  # noqa: F401
     version as __version__,
     version_tuple as __version_tuple__,
 )
-from .diffeq import DiffEqSolver
-from .interp import AbstractVectorizedDenseInterpolation, VectorizedDenseInterpolation
diff --git a/src/diffraxtra/_src/__init__.py b/src/diffraxtra/_src/__init__.py
new file mode 100644
index 0000000..904036f
--- /dev/null
+++ b/src/diffraxtra/_src/__init__.py
@@ -0,0 +1,13 @@
+"""Extras for `diffrax`. Private API."""
+
+__all__ = [
+    "DiffEqSolver",
+    "AbstractVectorizedDenseInterpolation",
+    "VectorizedDenseInterpolation",
+]
+
+from .diffeq import DiffEqSolver
+from .interp import (
+    AbstractVectorizedDenseInterpolation,
+    VectorizedDenseInterpolation,
+)
diff --git a/src/diffraxtra/diffeq.py b/src/diffraxtra/_src/diffeq.py
similarity index 100%
rename from src/diffraxtra/diffeq.py
rename to src/diffraxtra/_src/diffeq.py
diff --git a/src/diffraxtra/interp.py b/src/diffraxtra/_src/interp.py
similarity index 100%
rename from src/diffraxtra/interp.py
rename to src/diffraxtra/_src/interp.py