1 files changed, 1 insertions, 1 deletions
diff --git a/ice40/chains.cc b/ice40/chains.cc
index f75d329f..cfc8b4a1 100644
--- a/ice40/chains.cc
+++ b/ice40/chains.cc
@@ -253,7 +253,7 @@ class ChainConstrainer
                         return i3_next;
                     return (CellInfo *)nullptr;
                 });
-        std::unordered_set<IdString> chained;
+        pool<IdString> chained;
         for (auto &base_chain : carry_chains) {
             for (auto c : base_chain.cells)
                 chained.insert(c->name);