diff --git a/file.c b/file.c
index e65e548c9a..bf854d4df0 100644
--- a/file.c
+++ b/file.c
@@ -4035,7 +4035,7 @@ rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_na
 }
 #endif /* _WIN32 */
 
-#define EXPAND_PATH_BUFFER() rb_usascii_str_new(0, MAXPATHLEN + 2)
+#define EXPAND_PATH_BUFFER() rb_usascii_str_new(0, 1)
 
 static VALUE
 str_shrink(VALUE str)
diff --git a/test/ruby/test_file_exhaustive.rb b/test/ruby/test_file_exhaustive.rb
index 9ca991373e..a4f968be5f 100644
--- a/test/ruby/test_file_exhaustive.rb
+++ b/test/ruby/test_file_exhaustive.rb
@@ -874,7 +874,8 @@ class TestFileExhaustive < Test::Unit::TestCase
     path = File.expand_path("/foo")
     assert_operator(ObjectSpace.memsize_of(path), :<=, path.bytesize + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], bug9934)
     path = File.expand_path("/a"*25)
-    assert_equal(path.bytesize + 1 + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], ObjectSpace.memsize_of(path), bug9934)
+    assert_operator(ObjectSpace.memsize_of(path), :<=,
+                    (path.bytesize + 1) * 2 + GC::INTERNAL_CONSTANTS[:BASE_SLOT_SIZE], bug9934)
   end
 
   def test_expand_path_encoding