diff --git a/Library/Homebrew/bundle/cask_installer.rb b/Library/Homebrew/bundle/cask_installer.rb
index 781bbf57bf..4014666d73 100644
--- a/Library/Homebrew/bundle/cask_installer.rb
+++ b/Library/Homebrew/bundle/cask_installer.rb
@@ -41,7 +41,7 @@ module Homebrew
             case v
             when TrueClass
               "--#{k}"
-            when FalseClass
+            when FalseClass, NilClass
               nil
             else
               "--#{k}=#{v}"
diff --git a/Library/Homebrew/bundle/dsl.rb b/Library/Homebrew/bundle/dsl.rb
index 5196c17499..3431cc01c3 100644
--- a/Library/Homebrew/bundle/dsl.rb
+++ b/Library/Homebrew/bundle/dsl.rb
@@ -42,7 +42,7 @@ module Homebrew
       def cask_args(args)
         raise "cask_args(#{args.inspect}) should be a Hash object" unless args.is_a? Hash
 
-        @cask_arguments = args
+        @cask_arguments.merge!(args)
       end
 
       def brew(name, options = {})
diff --git a/Library/Homebrew/test/bundle/dsl_spec.rb b/Library/Homebrew/test/bundle/dsl_spec.rb
index 636bda3334..27f47bffd3 100644
--- a/Library/Homebrew/test/bundle/dsl_spec.rb
+++ b/Library/Homebrew/test/bundle/dsl_spec.rb
@@ -60,6 +60,20 @@ RSpec.describe Homebrew::Bundle::Dsl do
     end
   end
 
+  context "with multiple cask_args" do
+    subject(:dsl) do
+      dsl_from_string <<~EOS
+        cask_args appdir: '/global-apps'
+        cask_args require_sha: true
+        cask_args appdir: '~/my-apps'
+      EOS
+    end
+
+    it "merges the arguments" do
+      expect(dsl.cask_arguments).to eql(appdir: "~/my-apps", require_sha: true)
+    end
+  end
+
   context "with invalid input" do
     it "handles completely invalid code" do
       expect { dsl_from_string "abcdef" }.to raise_error(RuntimeError)