diff --git a/loopy/types.py b/loopy/types.py
index 59d605c85f3cfc54938cdb768529e747262050e6..0a08b8a815b1f35fae9aab1ff5aaca8696a8af80 100644
--- a/loopy/types.py
+++ b/loopy/types.py
@@ -199,6 +199,9 @@ class OpaqueType(LoopyType):
     def involves_complex(self):
         return False
 
+    def update_persistent_hash(self, key_hash, key_builder):
+        key_builder.rec(key_hash, self.name)
+
 # }}}