diff --git a/src/api/plugin.cpp b/src/api/plugin.cpp
index 63c031b2..02184e2a 100644
--- a/src/api/plugin.cpp
+++ b/src/api/plugin.cpp
@@ -195,7 +195,7 @@ bool Plugin::DoFormIDsOverlap(const PluginInterface& plugin) const {
 }
 
 size_t Plugin::GetOverlapSize(
-    const std::vector<const PluginInterface*> plugins) const {
+    const std::vector<const PluginInterface*>& plugins) const {
   if (plugins.empty()) {
     return 0;
   }
diff --git a/src/api/plugin.h b/src/api/plugin.h
index 174e9f4b..4112e1ef 100644
--- a/src/api/plugin.h
+++ b/src/api/plugin.h
@@ -47,7 +47,7 @@ public:
   virtual uint32_t GetRecordAndGroupCount() const = 0;
 
   virtual size_t GetOverlapSize(
-      const std::vector<const PluginInterface*> plugins) const = 0;
+      const std::vector<const PluginInterface*>& plugins) const = 0;
 };
 
 class Plugin final : public PluginSortingInterface {
@@ -73,7 +73,7 @@ public:
   bool LoadsArchive() const override;
   bool DoFormIDsOverlap(const PluginInterface& plugin) const override;
   size_t GetOverlapSize(
-      const std::vector<const PluginInterface*> plugins) const override;
+      const std::vector<const PluginInterface*>& plugins) const override;
 
   // Load ordering functions.
   size_t NumOverrideFormIDs() const override;