diff --git a/lib/thor/base.rb b/lib/thor/base.rb
index 442732876..cc7505143 100644
--- a/lib/thor/base.rb
+++ b/lib/thor/base.rb
@@ -9,7 +9,7 @@
 
 class Thor
   HELP_MAPPINGS       = %w(-h -? --help -D)
-  THOR_RESERVED_WORDS = %w(all invoke shell options behavior root destination_root relative_root source_root)
+  THOR_RESERVED_WORDS = %w(invoke shell options behavior root destination_root relative_root source_root)
 
   class Maxima < Struct.new(:usage, :options, :class_options)
   end
@@ -391,7 +391,7 @@ def class_options_help(shell, ungrouped_name=nil) #:nodoc:
         #
         def is_thor_reserved_word?(word, type)
           return false unless THOR_RESERVED_WORDS.include?(word.to_s)
-          raise ScriptError, "'#{word}' is a Thor reserved word and cannot be defined as #{type}"
+          raise "'#{word}' is a Thor reserved word and cannot be defined as #{type}"
         end
 
         # Build an option and adds it to the given scope.
diff --git a/spec/base_spec.rb b/spec/base_spec.rb
index 518c814d0..6a4067dc3 100644
--- a/spec/base_spec.rb
+++ b/spec/base_spec.rb
@@ -169,8 +169,9 @@ def hello
 
     it "raises an error if a task with reserved word is defined" do
       lambda {
-        MyCounter.class_eval "def all; end"
-      }.must raise_error(ScriptError, /'all' is a Thor reserved word and cannot be defined as task/)
+        klass = Class.new(Thor::Group)
+        klass.class_eval "def shell; end"
+      }.must raise_error(RuntimeError, /'shell' is a Thor reserved word and cannot be defined as task/)
     end
   end