diff --git a/plugins/stoa/lib/stoa_plugin/usp_user.rb b/plugins/stoa/lib/stoa_plugin/usp_user.rb
index 032c66a..ff11238 100644
--- a/plugins/stoa/lib/stoa_plugin/usp_user.rb
+++ b/plugins/stoa/lib/stoa_plugin/usp_user.rb
@@ -15,7 +15,7 @@ class StoaPlugin::UspUser < ActiveRecord::Base
   def self.matches?(usp_id, field, value)
     usp_id.to_s.gsub!(/[.-]/,'')
     user = StoaPlugin::UspUser.find_by_codpes(usp_id.to_i)
-    return false if user.nil? || !user.respond_to?(field) || value.blank?
+    return false if user.nil? || field.blank? || !user.respond_to?(field) || value.blank?
     case field.to_sym
     when :cpf
       value.to_s.gsub!(/[.-]/,'')
diff --git a/plugins/stoa/test/unit/usp_user_test.rb b/plugins/stoa/test/unit/usp_user_test.rb
index 2fa9704..e4a9481 100644
--- a/plugins/stoa/test/unit/usp_user_test.rb
+++ b/plugins/stoa/test/unit/usp_user_test.rb
@@ -43,5 +43,9 @@ class StoaPlugin::UspUserTest < ActiveSupport::TestCase
     assert  StoaPlugin::UspUser.exists?('0000123456')
     assert  StoaPlugin::UspUser.matches?(123456, :cpf, '00012345678')
   end
+
+  should 'return false if field is nil' do
+    assert  !StoaPlugin::UspUser.matches?(123456, nil, '00012345678')
+  end
 end
 
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libgit2 0.21.2