diff --git a/src/testing.c b/src/testing.c
index 8a64ce8..81e1762 100644
--- a/src/testing.c
+++ b/src/testing.c
@@ -883,6 +883,13 @@
 }
 
     void
+f_test_null_function(typval_T *argvars UNUSED, typval_T *rettv)
+{
+    rettv->v_type = VAR_FUNC;
+    rettv->vval.v_string = NULL;
+}
+
+    void
 f_test_null_partial(typval_T *argvars UNUSED, typval_T *rettv)
 {
     rettv->v_type = VAR_PARTIAL;