diff --git a/loopy/library/reduction.py b/loopy/library/reduction.py
index 091e4a2c1059e6f58b4b1768963b1f6337c3b17f..9a9b1c6e9ad5de6d0b21e1b432c2e4547373c490 100644
--- a/loopy/library/reduction.py
+++ b/loopy/library/reduction.py
@@ -444,7 +444,7 @@ class _ArgExtremumReductionOperation(ReductionOperation):
                 index_dtype.numpy_dtype.type(-1)), callables_table
 
     def __str__(self):
-        return self.which
+        return "arg" + self.which
 
     def __hash__(self):
         return hash(type(self))