diff --git a/sumpy/p2e.py b/sumpy/p2e.py
index dfb14755bc5144e7825587e570a2aad6e0e92b53..b6eb083d48eabdba124322791a8cc415d9de9e36 100644
--- a/sumpy/p2e.py
+++ b/sumpy/p2e.py
@@ -104,7 +104,8 @@ class P2EBase(KernelComputation, KernelCacheWrapper):
                 )
 
     def get_cache_key(self):
-        return (type(self).__name__, self.name, self.expansion)
+        return (type(self).__name__, self.name, self.expansion, tuple(self.kernels),
+                tuple(self.strength_usage))
 
     def get_result_expr(self, icoeff):
         expr = 0