diff --git a/lib/mutations/command.rb b/lib/mutations/command.rb
index c03cbbf..51fefe9 100644
--- a/lib/mutations/command.rb
+++ b/lib/mutations/command.rb
@@ -109,8 +109,16 @@ def execute
     # add_error("colors.foreground", :not_a_color) # => to create errors = {colors: {foreground: :not_a_color}}
     # or, supply a custom message:
     # add_error("name", :too_short, "The name 'blahblahblah' is too short!")
-    def add_error(key, kind, message = nil)
-      raise ArgumentError.new("Invalid kind") unless kind.is_a?(Symbol)
+    # or, supply an existing Mutations::ErrorHash or Mutations::ErrorArray:
+    # add_error("name", Mutations::ErrorArray.new([...]))
+    def add_error(key, error, message = nil)
+      if error.is_a? Symbol
+        error = ErrorAtom.new(key, error, message: message)
+      elsif error.is_a?(Mutations::ErrorAtom) || error.is_a?(Mutations::ErrorArray) || error.is_a?(Mutations::ErrorHash)
+
+      else
+        raise ArgumentError.new("Invalid error of kind #{error.class}")
+      end
 
       @errors ||= ErrorHash.new
       @errors.tap do |errs|
@@ -119,7 +127,7 @@ def add_error(key, kind, message = nil)
         inner = path.inject(errs) do |cur_errors,part|
           cur_errors[part.to_sym] ||= ErrorHash.new
         end
-        inner[last] = ErrorAtom.new(key, kind, :message => message)
+        inner[last] = error
       end
     end
 
diff --git a/spec/command_spec.rb b/spec/command_spec.rb
index 633abcc..9b656be 100644
--- a/spec/command_spec.rb
+++ b/spec/command_spec.rb
@@ -59,12 +59,12 @@
 
     it "should execute custom validate method during run" do
       outcome = SimpleCommand.run(:name => "JohnLong", :email => "xxxx")
-      
+
       assert !outcome.success?
       assert_nil outcome.result
       assert_equal :invalid, outcome.errors.symbolic[:email]
     end
-    
+
     it "should execute custom validate method only if regular validations succeed" do
       outcome = SimpleCommand.validate(:name => "JohnTooLong", :email => "xxxx")
 
@@ -217,6 +217,67 @@ def execute
     end
   end
 
+  describe "NestedErrorHashCommand" do
+    class NestedErrorHashCommand < Mutations::Command
+      required do
+        array :services do
+          model :object, class: Hash
+        end
+      end
+
+      def validate
+        service_errors = Mutations::ErrorHash.new
+        service_errors[:name] = Mutations::ErrorAtom.new(:name, :exists, message: "Service with name foo already exists")
+
+        add_error("services.foo", service_errors)
+      end
+    end
+
+    it "should let you add sub-mutation errors" do
+      outcome = NestedErrorHashCommand.run('services' => [
+          { 'name' => "foo" },
+      ])
+
+      assert !outcome.success?
+      assert_nil outcome.result
+      assert_equal({'services' => { 'foo' => { 'name' => :exists }}}, outcome.errors.symbolic)
+    end
+  end
+
+  describe "NestedErrorArrayCommand" do
+    class NestedErrorArrayCommand < Mutations::Command
+      required do
+        array :links do
+          hash do
+            required do
+              string :name
+            end
+          end
+        end
+      end
+
+      def validate
+        links_errors = Mutations::ErrorArray.new
+        links_errors << Mutations::ErrorAtom.new(:name, :not_found, message: "Link foo not found")
+        links_errors << Mutations::ErrorAtom.new(:name, :not_found, message: "Link bar not found")
+
+        add_error("links", links_errors)
+      end
+    end
+
+    it "should let you add sub-mutation errors" do
+      outcome = NestedErrorArrayCommand.run('links' => [
+          { 'name' => "foo" },
+          { 'name' => "bar" },
+      ])
+
+      assert !outcome.success?
+      assert_nil outcome.result
+      assert_equal({'links' => [:not_found, :not_found]}, outcome.errors.symbolic)
+      assert_equal({'links' => ["Link foo not found", "Link bar not found"]}, outcome.errors.message)
+    end
+  end
+
   describe "PresentCommand" do
     class PresentCommand < Mutations::Command