diff --git a/ChangeLog b/ChangeLog
index d42b9690de..1213644718 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Jul  2 18:04:24 2016  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* lib/uri/mailto.rb (initialize): RFC3986_Parser#split sets opaque
+	  only if the URI has path-rootless, not path-empty.
+	  [ruby-core:76055] [Bug #12498]
+	  patched by Chris Heisterkamp <cheister@squareup.com>
+
 Sat Jul  2 04:26:14 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* regcomp.c (noname_disable_map): don't optimize out group 0
diff --git a/lib/uri/mailto.rb b/lib/uri/mailto.rb
index 495f939a3b..7299550d3f 100644
--- a/lib/uri/mailto.rb
+++ b/lib/uri/mailto.rb
@@ -136,6 +136,9 @@ module URI
       @to = nil
       @headers = []
 
+      # The RFC3986 parser does not normally populate opaque
+      @opaque = "?#{@query}" if @query && !@opaque
+
       unless @opaque
         raise InvalidComponentError,
           "missing opaque part for mailto URL"
diff --git a/test/uri/test_mailto.rb b/test/uri/test_mailto.rb
index 4e3b0425fa..c09b001e0f 100644
--- a/test/uri/test_mailto.rb
+++ b/test/uri/test_mailto.rb
@@ -112,13 +112,15 @@ class TestMailTo < Test::Unit::TestCase
     bad << ["foo@example.jp?subject=1+1=2", []]
 
     ok.each do |x|
-      assert_equal(x[0],
-		   @u.build(x[1]).to_s)
-      assert_equal(x[0],
-		   @u.build(x[2]).to_s)
+      assert_equal(x[0], URI.parse(x[0]).to_s)
+      assert_equal(x[0], @u.build(x[1]).to_s)
+      assert_equal(x[0], @u.build(x[2]).to_s)
     end
 
     bad.each do |x|
+      assert_raise(URI::InvalidURIError) {
+        URI.parse(x)
+      }
       assert_raise(URI::InvalidComponentError) {
 	@u.build(x)
       }