diff --git a/loopy/kernel/tools.py b/loopy/kernel/tools.py
index 2f2e9a8a9..4a3f40bd6 100644
--- a/loopy/kernel/tools.py
+++ b/loopy/kernel/tools.py
@@ -1491,7 +1491,7 @@ def stringify_instruction_tag(tag):
         return str(tag)
 
 
-def stringify_instruction_list(kernel):
+def stringify_instruction_list(kernel: LoopKernel) -> str:
     # {{{ topological sort
 
     printed_insn_ids = set()