diff --git a/python/dune/codegen/ufl/visitor.py b/python/dune/codegen/ufl/visitor.py
index e55232d26839abb2a8866dc2a57af715156237a7..ab7c334f323bbc51221d926d357466d6ebc8cf88 100644
--- a/python/dune/codegen/ufl/visitor.py
+++ b/python/dune/codegen/ufl/visitor.py
@@ -264,6 +264,7 @@ class UFL2LoopyVisitor(ModifiedTerminalTracker):
 
     def identity(self, o):
         i, j = self.indices
+        self.indices = None
         assert isinstance(i, int) and isinstance(j, int)
         return 1 if i == j else 0