diff --git a/Library/Homebrew/rubocops/text_cop.rb b/Library/Homebrew/rubocops/text_cop.rb
index 1546a9cc3c..701cb548f4 100644
--- a/Library/Homebrew/rubocops/text_cop.rb
+++ b/Library/Homebrew/rubocops/text_cop.rb
@@ -48,6 +48,11 @@ module RuboCop
           find_method_with_args(body_node, :system, "go", "get") do
             problem "Do not use `go get`. Please ask upstream to implement Go vendoring"
           end
+
+          find_method_with_args(body_node, :system, "dep", "ensure") do |d|
+            next if parameters_passed?(d, /vendor-only/)
+            problem "use \"dep\", \"ensure\", \"-vendor-only\""
+          end
         end
       end
     end
diff --git a/Library/Homebrew/test/rubocops/text_cop_spec.rb b/Library/Homebrew/test/rubocops/text_cop_spec.rb
index 1b2d61d0c8..52881bfa13 100644
--- a/Library/Homebrew/test/rubocops/text_cop_spec.rb
+++ b/Library/Homebrew/test/rubocops/text_cop_spec.rb
@@ -177,5 +177,19 @@ describe RuboCop::Cop::FormulaAudit::Text do
         end
       RUBY
     end
+
+    it "When dep ensure is used without `-vendor-only`" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "http://example.com/foo-1.0.tgz"
+          homepage "http://example.com"
+
+          def install
+            system "dep", "ensure"
+            ^^^^^^^^^^^^^^^^^^^^^^ use \"dep\", \"ensure\", \"-vendor-only\"
+          end
+        end
+      RUBY
+    end
   end
 end