diff --git a/ext/pathname/lib/pathname.rb b/ext/pathname/lib/pathname.rb
index a6621565d0..8bdb73f439 100644
--- a/ext/pathname/lib/pathname.rb
+++ b/ext/pathname/lib/pathname.rb
@@ -378,7 +378,7 @@ class Pathname
       basename_list2.shift
     end
     r1 = chop_basename(prefix1)
-    if !r1 && /#{SEPARATOR_PAT}/o =~ File.basename(prefix1)
+    if !r1 && (r1 = /#{SEPARATOR_PAT}/o =~ File.basename(prefix1))
       while !basename_list2.empty? && basename_list2.first == '..'
         index_list2.shift
         basename_list2.shift
diff --git a/test/pathname/test_pathname.rb b/test/pathname/test_pathname.rb
index 848d4e4190..1efd40121d 100644
--- a/test/pathname/test_pathname.rb
+++ b/test/pathname/test_pathname.rb
@@ -14,8 +14,8 @@ class TestPathname < Test::Unit::TestCase
   end
 
   def self.get_linenum
-    if /:(\d+):/ =~ caller[1]
-      $1.to_i
+    if loc = caller_locations(2, 1)
+      loc[0].lineno
     else
       nil
     end
@@ -221,6 +221,8 @@ class TestPathname < Test::Unit::TestCase
 
   defassert(:plus, 'a//b/d//e', 'a//b/c', '../d//e')
 
+  defassert(:plus, '//foo/var/bar', '//foo/var', 'bar')
+
   def test_slash
     assert_kind_of(Pathname, Pathname("a") / Pathname("b"))
   end