diff --git a/third_party/nix/src/libexpr/symbol-table.hh b/third_party/nix/src/libexpr/symbol-table.hh
index df696c9e1..c4c1163be 100644
--- a/third_party/nix/src/libexpr/symbol-table.hh
+++ b/third_party/nix/src/libexpr/symbol-table.hh
@@ -19,7 +19,7 @@ class Symbol {
 
   bool operator!=(const Symbol& s2) const { return s != s2.s; }
 
-  bool operator<(const Symbol& s2) const { return s < s2.s; }
+  bool operator<(const Symbol& s2) const { return *s < *s2.s; }
 
   operator const std::string&() const { return *s; }