diff --git a/sumpy/kernel.py b/sumpy/kernel.py
index 7324a082f166b21bc46aa4b95fa6be9dfbb2168e..cf0835de455ec0aecbc03a809aa8bae5a28c9160 100644
--- a/sumpy/kernel.py
+++ b/sumpy/kernel.py
@@ -26,7 +26,7 @@ from six.moves import range, zip
 
 import loopy as lp
 import numpy as np
-from pymbolic.mapper import IdentityMapper
+from pymbolic.mapper import IdentityMapper, CSECachingMapperMixin
 from sumpy.symbolic import pymbolic_real_norm_2
 from pymbolic.primitives import make_sym_vector
 from pymbolic import var
@@ -652,7 +652,7 @@ class AxisTargetDerivative(DerivativeBase):
     mapper_method = "map_axis_target_derivative"
 
 
-class _VectorIndexAdder(IdentityMapper):
+class _VectorIndexAdder(CSECachingMapperMixin, IdentityMapper):
     def __init__(self, vec_name, additional_indices):
         self.vec_name = vec_name
         self.additional_indices = additional_indices
@@ -666,6 +666,8 @@ class _VectorIndexAdder(IdentityMapper):
         else:
             return IdentityMapper.map_subscript(self, expr)
 
+    map_common_subexpression_uncached = IdentityMapper.map_common_subexpression
+
 
 class DirectionalDerivative(DerivativeBase):
     init_arg_names = ("inner_kernel", "dir_vec_name")