diff --git a/Library/Homebrew/caveats.rb b/Library/Homebrew/caveats.rb
index 2032e9ff1a..ee09063fd9 100644
--- a/Library/Homebrew/caveats.rb
+++ b/Library/Homebrew/caveats.rb
@@ -46,7 +46,7 @@ class Caveats
 
     s = <<-EOS.undent
       This formula is keg-only, which means it was not symlinked into #{HOMEBREW_PREFIX},
-      because #{f.keg_only_reason}.
+      because #{f.keg_only_reason.to_s.chomp}.
     EOS
     if f.bin.directory? || f.sbin.directory?
       s << "\nIf you need to have this software first in your PATH run:\n"
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index be53e1d6fd..1081fa0ba5 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -502,6 +502,7 @@ class FormulaAuditor
       GPG
       GNOME
       BSD
+      Firefox
     ].freeze
 
     reason = formula.keg_only_reason.to_s
@@ -510,7 +511,7 @@ class FormulaAuditor
     reason.sub!(name, "")
     first_word = reason.split[0]
 
-    if reason =~ /^[A-Z]/ && !reason.start_with?(*whitelist)
+    if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
       problem <<-EOS.undent
         '#{first_word}' from the keg_only reason should be '#{first_word.downcase}'.
       EOS
diff --git a/Library/Homebrew/test/dev-cmd/audit_spec.rb b/Library/Homebrew/test/dev-cmd/audit_spec.rb
index 771e1ee799..c914a9a201 100644
--- a/Library/Homebrew/test/dev-cmd/audit_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/audit_spec.rb
@@ -322,6 +322,69 @@ describe FormulaAuditor do
       .to eq(["Don't recommend setuid in the caveats, suggest sudo instead."])
   end
 
+  describe "#audit_keg_only_style" do
+    specify "keg_only_needs_downcasing" do
+      fa = formula_auditor "foo", <<-EOS.undent, strict: true
+        class Foo < Formula
+          url "http://example.com/foo-1.0.tgz"
+
+          keg_only "Because why not"
+        end
+      EOS
+
+      fa.audit_keg_only_style
+      expect(fa.problems)
+        .to eq(["'Because' from the keg_only reason should be 'because'.\n"])
+    end
+
+    specify "keg_only_redundant_period" do
+      fa = formula_auditor "foo", <<-EOS.undent, strict: true
+        class Foo < Formula
+          url "http://example.com/foo-1.0.tgz"
+
+          keg_only "because this line ends in a period."
+        end
+      EOS
+
+      fa.audit_keg_only_style
+      expect(fa.problems)
+        .to eq(["keg_only reason should not end with a period."])
+    end
+
+    specify "keg_only_handles_block_correctly" do
+      fa = formula_auditor "foo", <<-EOS.undent, strict: true
+        class Foo < Formula
+          url "http://example.com/foo-1.0.tgz"
+
+          keg_only <<-EOF.undent
+            this line starts with a lowercase word.
+
+            This line does not but that shouldn't be a
+            problem
+          EOF
+        end
+      EOS
+
+      fa.audit_keg_only_style
+      expect(fa.problems)
+        .to eq([])
+    end
+
+    specify "keg_only_handles_whitelist_correctly" do
+      fa = formula_auditor "foo", <<-EOS.undent, strict: true
+        class Foo < Formula
+          url "http://example.com/foo-1.0.tgz"
+
+          keg_only "Apple ships foo in the CLT package"
+        end
+      EOS
+
+      fa.audit_keg_only_style
+      expect(fa.problems)
+        .to eq([])
+    end
+  end
+
   describe "#audit_homepage" do
     specify "homepage URLs" do
       fa = formula_auditor "foo", <<-EOS.undent, online: true