1 files changed, 5 insertions, 0 deletions
diff --git a/src/libexpr/primops/flakeref.hh b/src/libexpr/primops/flakeref.hh
index d789a6f70..e599e2feb 100644
--- a/src/libexpr/primops/flakeref.hh
+++ b/src/libexpr/primops/flakeref.hh
@@ -1,3 +1,5 @@
+#pragma once
+
 #include "types.hh"
 #include "hash.hh"
 
@@ -173,4 +175,7 @@ struct FlakeRef
 
     FlakeRef baseRef() const;
 };
+
+std::ostream & operator << (std::ostream & str, const FlakeRef & flakeRef);
+
 }