diff --git a/src/error.cpp b/src/error.cpp
index 11fa671..fc85bf2 100644
--- a/src/error.cpp
+++ b/src/error.cpp
@@ -23,7 +23,7 @@
 
 static std::vector<std::string> errors;
 
-void add_error(std::string error) {
+void add_error(const std::string &error) {
 	if(not errors.empty())
 		errors.push_back(error);
 }
diff --git a/src/error.hpp b/src/error.hpp
index 8be0e4f..b031011 100644
--- a/src/error.hpp
+++ b/src/error.hpp
@@ -20,4 +20,4 @@
 
 #include <string>
 
-void add_error(std::string error);
+void add_error(const std::string &error);