diff --git a/pymbolic/mapper/stringifier.py b/pymbolic/mapper/stringifier.py
index c379c04f4403d763b09a488921e5015fe961fdd3..65c991a0eaf048cd5d98e641e59e51f6e7057715 100644
--- a/pymbolic/mapper/stringifier.py
+++ b/pymbolic/mapper/stringifier.py
@@ -138,6 +138,8 @@ class StringifyMapper(pymbolic.mapper.Mapper):
         return self.parenthesize_if_needed(
                 self.format("%s[%s]",
                     self.rec(expr.aggregate, PREC_CALL),
+                    self.join_rec(", ", expr.index, PREC_NONE) if
+                    isinstance(expr.index, tuple) else
                     self.rec(expr.index, PREC_NONE)),
                 enclosing_prec, PREC_CALL)