diff --git a/src/if_py_both.h b/src/if_py_both.h
index 4a32124..0620171 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -105,7 +105,7 @@
 # define Py_TYPE_GET_TP_METHODS(type) ((PyMethodDef *)PyType_GetSlot(type, Py_tp_methods))
 
 // PyObject_NEW is not part of stable ABI, but PyObject_Malloc/Init are.
-PyObject* Vim_PyObject_New(PyTypeObject *type, size_t objsize)
+static PyObject* Vim_PyObject_New(PyTypeObject *type, size_t objsize)
 {
     PyObject *obj = (PyObject *)PyObject_Malloc(objsize);
     if (obj == NULL)
@@ -168,7 +168,7 @@
 #  define PyIter_Check(obj) (FALSE)
 # endif
 
-PyTypeObject* AddHeapType(struct typeobject_wrapper* type_object)
+static PyTypeObject* AddHeapType(struct typeobject_wrapper* type_object)
 {
     PyType_Spec type_spec;
     type_spec.name = type_object->tp_name;
@@ -254,7 +254,7 @@
 
 // Limited API does not provide PyRun_* functions. Need to implement manually
 // using PyCompile and PyEval.
-PyObject* Vim_PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
+static PyObject* Vim_PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
 {
     // Just pass "" for filename for now.
     PyObject* compiled = Py_CompileString(str, "", start);
@@ -265,7 +265,7 @@
     Py_DECREF(compiled);
     return eval_result;
 }
-int Vim_PyRun_SimpleString(const char *str)
+static int Vim_PyRun_SimpleString(const char *str)
 {
     // This function emulates CPython's implementation.
     PyObject* m = PyImport_AddModule("__main__");