diff --git a/nixos/modules/installer/tools/nixos-option/nixos-option.cc b/nixos/modules/installer/tools/nixos-option/nixos-option.cc
index fc9315423dd..536d67c2d09 100644
--- a/nixos/modules/installer/tools/nixos-option/nixos-option.cc
+++ b/nixos/modules/installer/tools/nixos-option/nixos-option.cc
@@ -140,7 +140,7 @@ bool isOption(Context * ctx, const Value & v)
         if (evaluated_type.type != tString) {
             return false;
         }
-        return evaluated_type.string.s == static_cast<std::string>("option");
+        return static_cast<std::string>(evaluated_type.string.s) == "option";
     } catch (Error &) {
         return false;
     }