diff --git a/libyul/optimiser/CommonSubexpressionEliminator.cpp b/libyul/optimiser/CommonSubexpressionEliminator.cpp
index 2f80e7bc4..6a739618c 100644
--- a/libyul/optimiser/CommonSubexpressionEliminator.cpp
+++ b/libyul/optimiser/CommonSubexpressionEliminator.cpp
@@ -103,9 +103,9 @@ void CommonSubexpressionEliminator::visit(Expression& _e)
 		for (auto const& [variable, value]: m_value)
 		{
 			assertThrow(value.value, OptimizerException, "");
-			assertThrow(inScope(variable), OptimizerException, "");
 			if (SyntacticallyEqual{}(_e, *value.value))
 			{
+				assertThrow(inScope(variable), OptimizerException, "");
 				_e = Identifier{locationOf(_e), variable};
 				break;
 			}