diff --git a/src/util/file.cpp b/src/util/file.cpp
index ee84c57..ecaa8cd 100644
--- a/src/util/file.cpp
+++ b/src/util/file.cpp
@@ -60,7 +60,7 @@ void File::clear()
 	m_data.clear();
 }
 
-File& File::append(std::string data)
+File& File::append(const std::string& data)
 {
 	m_data.append(data);
 
diff --git a/src/util/file.h b/src/util/file.h
index fcbb90b..802acf5 100644
--- a/src/util/file.h
+++ b/src/util/file.h
@@ -19,7 +19,7 @@ public:
 	static File create(const std::string& path);
 
 	void clear();
-	File& append(std::string data);
+	File& append(const std::string& data);
 	File& replace(size_t index, size_t length, const std::string& data);
 	File& flush();