diff --git a/src/libexpr/primops/flakeref.cc b/src/libexpr/primops/flakeref.cc
index 3842b3f1a..c42616374 100644
--- a/src/libexpr/primops/flakeref.cc
+++ b/src/libexpr/primops/flakeref.cc
@@ -194,6 +194,8 @@ std::string FlakeRef::to_string() const
 
     else abort();
 
+    assert(FlakeRef(string) == *this);
+
     return string;
 }