diff --git a/UPGRADING.md b/UPGRADING.md
index 4b4ed33..34c2416 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -1,5 +1,7 @@
 ## HEAD
 
+* No longer raises `Pavlov::ValidationError, "Missing arguments:` when an argument is nil but adds an error.
+
 # 0.1.8
 
 * Let custom validations use errors.add instead of raising exceptions
diff --git a/lib/pavlov/operation.rb b/lib/pavlov/operation.rb
index 3d02276..4ec3949 100644
--- a/lib/pavlov/operation.rb
+++ b/lib/pavlov/operation.rb
@@ -51,13 +51,15 @@ def raise_unauthorized(message = 'Unauthorized')
     end
 
     def check_validation
-      fail Pavlov::ValidationError, "Missing arguments: #{missing_arguments.inspect}" if missing_arguments.any?
+      check_missing_arguments
       validate
     end
 
-    def missing_arguments
-      attribute_set.select do |attribute|
-        !attribute.options.key?(:default) && send(attribute.name).nil?
+    def check_missing_arguments
+      attribute_set.each do |attribute|
+        if !attribute.options.key?(:default) && send(attribute.name).nil?
+          errors.add(attribute.name.to_s, "can't be blank")
+        end
       end
     end
 
diff --git a/spec/regression/case2_spec.rb b/spec/regression/case2_spec.rb
index 834886b..89570c9 100755
--- a/spec/regression/case2_spec.rb
+++ b/spec/regression/case2_spec.rb
@@ -28,7 +28,7 @@ def list
       def members_to_remove
         list.zrange(0, -1).select do |id|
           activity = Activity[id]
-          ! valid(activity)
+          !valid(activity)
         end
       end
 
diff --git a/spec/regression/case4_spec.rb b/spec/regression/case4_spec.rb
index 21599cf..3b0ada0 100644
--- a/spec/regression/case4_spec.rb
+++ b/spec/regression/case4_spec.rb
@@ -15,7 +15,7 @@ class Interactors::ExampleModule::FollowUser
       arguments :user_name, :user_to_follow_user_name
 
       def authorized?
-        (!! pavlov_options[:current_user]) && (pavlov_options[:current_user].username == user_name)
+        (!!pavlov_options[:current_user]) && (pavlov_options[:current_user].username == user_name)
       end
 
       def user
diff --git a/spec/regression/case5_spec.rb b/spec/regression/case5_spec.rb
index df7e33a..35f3352 100644
--- a/spec/regression/case5_spec.rb
+++ b/spec/regression/case5_spec.rb
@@ -15,7 +15,7 @@ class Interactors::ExampleModule::Followers
       arguments :user_name, :skip, :take
 
       def authorized?
-        !! pavlov_options[:current_user]
+        !!pavlov_options[:current_user]
       end
 
       def validate