diff --git a/src/frontend/ir/ir.cpp b/src/frontend/ir/ir.cpp
index d14a45d4..d8b6ec61 100644
--- a/src/frontend/ir/ir.cpp
+++ b/src/frontend/ir/ir.cpp
@@ -189,7 +189,7 @@ std::string DumpBlock(const IR::Block& block) {
         }
 
         ret += "\n";
-        inst_to_index.at(&*inst) = index++;
+        inst_to_index[&*inst] = index++;
     }
 
     return ret;