diff --git a/Library/Homebrew/formula_support.rb b/Library/Homebrew/formula_support.rb
index 6813c1faa247cfbd5a0dbc442c5bf86579ef3b69..f6bb000bc2a8b4d6958047998c86bcc76d54f836 100644
--- a/Library/Homebrew/formula_support.rb
+++ b/Library/Homebrew/formula_support.rb
@@ -23,28 +23,23 @@ class KegOnlyReason
   end
 
   def to_s
+    return @explanation unless @explanation.empty?
     case @reason
     when :provided_by_osx then <<-EOS
 OS X already provides this software and installing another version in
 parallel can cause all kinds of trouble.
-
-#{@explanation}
 EOS
     when :shadowed_by_osx then <<-EOS
 OS X provides similar software, and installing this software in
 parallel can cause all kinds of trouble.
-
-#{@explanation}
 EOS
     when :provided_pre_mountain_lion then <<-EOS
 OS X already provides this software in versions before Mountain Lion.
-
-#{@explanation}
 EOS
     when :provided_until_xcode43
-      "Xcode provides this software prior to version 4.3.\n\n#{@explanation}"
+      "Xcode provides this software prior to version 4.3."
     when :provided_until_xcode5
-      "Xcode provides this software prior to version 5.\n\n#{@explanation}"
+      "Xcode provides this software prior to version 5."
     else
       @reason
     end.strip
diff --git a/Library/Homebrew/test/test_formula_support.rb b/Library/Homebrew/test/test_formula_support.rb
new file mode 100644
index 0000000000000000000000000000000000000000..08d10292f29917a3ecdd9967aabd119ea6115ab0
--- /dev/null
+++ b/Library/Homebrew/test/test_formula_support.rb
@@ -0,0 +1,13 @@
+require "testing_env"
+
+class KegOnlyReasonTests < Homebrew::TestCase
+  def test_to_s_explanation
+    r = KegOnlyReason.new :provided_by_osx, "test"
+    assert_equal "test", r.to_s
+  end
+
+  def test_to_s_no_explanation
+    r = KegOnlyReason.new :provided_by_osx, ""
+    assert_match(/^OS X already provides/, r.to_s)
+  end
+end