diff --git a/to-edn.nix b/to-edn.nix
index 7b37e0c..b5c3487 100644
--- a/to-edn.nix
+++ b/to-edn.nix
@@ -2,7 +2,7 @@
 
 with lib;
 let
-  isSymbol = str: isNull (builtins.match "^'.+" str);
+  isSymbol = str: !(isNull (builtins.match "^'.+" str));
   stripQuote = str: head (builtins.match "^'(.+)" str);
   parseStr = str: if (isSymbol str) then (stripQuote str) else ''"${str}"'';