diff --git a/Library/Homebrew/cli/args.rb b/Library/Homebrew/cli/args.rb
index 01215dd20a..414448fcb7 100644
--- a/Library/Homebrew/cli/args.rb
+++ b/Library/Homebrew/cli/args.rb
@@ -135,7 +135,7 @@ module Homebrew
       end
 
       def respond_to_missing?(method_name, *)
-        !frozen? || @table.key?(method_name)
+        @table.key?(method_name)
       end
 
       def method_missing(method_name, *args)
diff --git a/Library/Homebrew/test/cli/named_args_spec.rb b/Library/Homebrew/test/cli/named_args_spec.rb
index 00b55fafc1..e69eb4bb2b 100644
--- a/Library/Homebrew/test/cli/named_args_spec.rb
+++ b/Library/Homebrew/test/cli/named_args_spec.rb
@@ -118,12 +118,6 @@ describe Homebrew::CLI::NamedArgs do
       expect { described_class.new("foo").to_formulae_and_casks }.to raise_error(FormulaOrCaskUnavailableError)
     end
 
-    it "raises an error when formula is absent and cask is available on linux", :needs_linux do
-      stub_cask_loader foo_cask
-
-      expect { described_class.new("foo").to_formulae_and_casks }.to raise_error(FormulaUnavailableError)
-    end
-
     it "returns formula when formula is present and cask is unreadable", :needs_macos do
       stub_formula_loader foo
       setup_unredable_cask "foo"
@@ -311,12 +305,6 @@ describe Homebrew::CLI::NamedArgs do
 
       expect(described_class.new("foo", "baz").to_paths(only: :cask)).to eq [cask_path, Cask::CaskLoader.path("baz")]
     end
-
-    it "returns only formulae by default on linux", :needs_linux do
-      expect(Formulary).to receive(:path).with("foo").and_return(formula_path)
-
-      expect(described_class.new("foo", "baz").to_paths).to eq [formula_path, Formulary.path("baz")]
-    end
   end
 
   describe "#to_taps" do
diff --git a/Library/Homebrew/test/cli/parser_spec.rb b/Library/Homebrew/test/cli/parser_spec.rb
index ce670b2f25..b2983a09bb 100644
--- a/Library/Homebrew/test/cli/parser_spec.rb
+++ b/Library/Homebrew/test/cli/parser_spec.rb
@@ -570,12 +570,24 @@ describe Homebrew::CLI::Parser do
       end
     end
 
-    it "throws an error by default" do
+    it "throws an error when defined" do
       expect { parser.parse(["--cask"]) }.to raise_error UsageError, /Casks are not supported on Linux/
     end
+  end
 
-    it "only warns developers", :needs_macos do
-      expect { parser.parse(["--cask"]) }.not_to raise_error
+  describe "--formula on linux", :needs_linux do
+    it "doesn't set --formula when not defined" do
+      parser = described_class.new
+      args = parser.parse([])
+      expect(args.respond_to?(:formula?)).to be(false)
+    end
+
+    it "sets --formula to true when defined" do
+      parser = described_class.new do
+        switch "--formula"
+      end
+      args = parser.parse([])
+      expect(args.formula?).to be(true)
     end
   end
 end