diff --git a/src/spectator/double.cr b/src/spectator/double.cr
index 8e4237d..aeed0c1 100644
--- a/src/spectator/double.cr
+++ b/src/spectator/double.cr
@@ -5,7 +5,11 @@ module Spectator
 
       private class Internal
         def {{definition.name.id}}({{definition.args.splat}})
-          {{definition.block.body}}
+          {% if definition.block.is_a?(Nop) %}
+            raise "Stubbed method called without being allowed"
+          {% else %}
+            {{definition.block.body}}
+          {% end %}
         end
       end
     end