diff --git a/nib/types/terminal.nix b/nib/types/terminal.nix
index a3b37a9..9e996ea 100644
--- a/nib/types/terminal.nix
+++ b/nib/types/terminal.nix
@@ -8,7 +8,8 @@
 
   # Pattern Matching
   isTerminal = T:
-    (builtins.attrNames T == ["_nbtype_" "_value_"])
+    builtins.isAttrs T
+    && builtins.attrNames T == ["_nbtype_" "_value_"]
     && T._nbtype_ == "nib::Terminal";
 
   # Unwrap (Monadic Return Operation)