diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 876ebf38460..5163070b2e6 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -108,7 +108,7 @@ struct StoreConfig : public StoreDirConfig
 
     StoreConfig() = delete;
 
-    StringSet getDefaultSystemFeatures();
+    static StringSet getDefaultSystemFeatures();
 
     virtual ~StoreConfig() { }