diff --git a/loopy/kernel/instruction.py b/loopy/kernel/instruction.py
index 3221535ae5b25fa117035ed1f8fca7a808bcc213..b409f446b8b2b057b26e37df2120a62967397f92 100644
--- a/loopy/kernel/instruction.py
+++ b/loopy/kernel/instruction.py
@@ -160,6 +160,9 @@ class InstructionBase(Record):
             within_inames = forced_iname_deps
             within_inames_is_final = forced_iname_deps_is_final
 
+        if predicates is None:
+            predicates = frozenset()
+
         new_predicates = set()
         for pred in predicates:
             if isinstance(pred, str):