diff --git a/sumpy/kernel.py b/sumpy/kernel.py
index d4c45a4b6317bdf006ff1f46c771330c12faf422..859b2dbdebe3773243cd0bea6cfcc6b2d9a07eed 100644
--- a/sumpy/kernel.py
+++ b/sumpy/kernel.py
@@ -239,7 +239,7 @@ class Kernel:
         The typical use of this function is to apply target-variable
         derivatives to the kernel.
 
-        :arg expr: may be a :class:`sympy.Expr` or a
+        :arg expr: may be a :class:`sympy.core.expr.Expr` or a
             :class:`sumpy.tools.DifferentiatedExprDerivativeTaker`.
         """
         return expr