diff --git a/libyul/Object.cpp b/libyul/Object.cpp
index 032e828bd..12b964e80 100644
--- a/libyul/Object.cpp
+++ b/libyul/Object.cpp
@@ -190,7 +190,7 @@ std::vector<size_t> Object::pathToSubObject(YulString _qualifiedName) const
 	return path;
 }
 
-Object const* Object::subObjectAt(std::string const& _qualifiedName)
+Object const* Object::subObjectAt(YulString _qualifiedName)
 {
 	if (_qualifiedName.empty())
 		return nullptr;
@@ -198,14 +198,14 @@ Object const* Object::subObjectAt(std::string const& _qualifiedName)
 	// If there is no `.` in the given `_qualifiedName`, the target
 	// object name is considered to be the `_qualifiedName`, otherwise,
 	// the target object name is the last element in the path given by `_qualifiedName`.
-	std::string targetObjectName = _qualifiedName;
-	size_t targetObjectPos = _qualifiedName.find_last_of(".");
+	YulString targetObjectName = _qualifiedName;
+	size_t targetObjectPos = _qualifiedName.str().find_last_of(".");
 	if (targetObjectPos != std::string::npos)
-		targetObjectName = _qualifiedName.substr(targetObjectPos + 1);
+		targetObjectName = YulString(_qualifiedName.str().substr(targetObjectPos + 1));
 
 	Object const* foundObject = nullptr;
-	this->visitPath(YulString(_qualifiedName), [&](Object const* _subObject) -> bool {
-		if (targetObjectName != _subObject->name.str())
+	this->visitPath(_qualifiedName, [&](Object const* _subObject) -> bool {
+		if (targetObjectName != _subObject->name)
 			return false;
 		foundObject = _subObject;
 		return true;
diff --git a/libyul/Object.h b/libyul/Object.h
index c9fd65826..4a97870a5 100644
--- a/libyul/Object.h
+++ b/libyul/Object.h
@@ -119,7 +119,7 @@ public:
 
 	/// Searches for a subobject at @param _qualifiedName within the current object.
 	/// @returns a pointer to the subobject or a nullptr if it was not found.
-	Object const* subObjectAt(std::string const& _qualifiedName);
+	Object const* subObjectAt(YulString _qualifiedName);
 
 	/// Visits all subobjects in the path given by the @a _qualifiedName
 	/// of the current object applying the function @a _visitor.
diff --git a/test/tools/yulopti.cpp b/test/tools/yulopti.cpp
index b8bba823d..300d9d940 100644
--- a/test/tools/yulopti.cpp
+++ b/test/tools/yulopti.cpp
@@ -253,7 +253,7 @@ public:
 	{
 		if (!m_inputIsCodeBlock)
 		{
-			Object const* subObject = m_object->subObjectAt(_objectPath);
+			Object const* subObject = m_object->subObjectAt(YulString(_objectPath));
 
 			if (subObject == nullptr)
 				solThrow(Exception, "Assembly object not found.");