diff --git a/sumpy/kernel.py b/sumpy/kernel.py
index 859b2dbde..1db8f11c7 100644
--- a/sumpy/kernel.py
+++ b/sumpy/kernel.py
@@ -1077,6 +1077,10 @@ class DirectionalDerivative(DerivativeBase):
     def __init__(self, inner_kernel, dir_vec_name=None):
         if dir_vec_name is None:
             dir_vec_name = self.directional_kind + "_derivative_dir"
+        else:
+            from warnings import warn
+            warn("specified the name of the direction vector",
+                    stacklevel=2)
 
         KernelWrapper.__init__(self, inner_kernel)
         self.dir_vec_name = dir_vec_name