diff --git a/include/xlnt/packaging/relationship.hpp b/include/xlnt/packaging/relationship.hpp
index 09e88ff2..2dcbb4af 100644
--- a/include/xlnt/packaging/relationship.hpp
+++ b/include/xlnt/packaging/relationship.hpp
@@ -115,7 +115,7 @@ public:
     /// <summary>
     /// Returns a string of the form rId# that identifies the relationship.
     /// </summary>
-    std::string id() const;
+    const std::string& id() const;
 
     /// <summary>
     /// Returns the type of this relationship.
diff --git a/source/packaging/relationship.cpp b/source/packaging/relationship.cpp
index 07f7bafa..9c104e08 100644
--- a/source/packaging/relationship.cpp
+++ b/source/packaging/relationship.cpp
@@ -36,7 +36,7 @@ relationship::relationship(
 {
 }
 
-std::string relationship::id() const
+const std::string& relationship::id() const
 {
     return id_;
 }