diff --git a/src/exception.hh b/src/exception.hh
index f341e724..89188e63 100644
--- a/src/exception.hh
+++ b/src/exception.hh
@@ -14,7 +14,7 @@ struct exception
 
 struct runtime_error : exception
 {
-    runtime_error(const std::string description)
+    runtime_error(const std::string& description)
         : m_description(description) {}
 
     std::string description() const { return m_description; }