diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 4eb1511..c49c4a8 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -1187,9 +1187,7 @@ prepare_getline_args(struct StringIO *ptr, struct getline_arg *arg, int argc, VA
                 rs = rs;
             }
             else {
-                rb_raise(rb_eArgError, "encoding mismatch: %s IO with %s RS",
-                         rb_enc_name(enc_io),
-                         rb_enc_name(enc_rs));
+		rs = rb_str_conv_enc(rs, enc_rs, enc_io);
             }
         }
     }
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index 15fcc21..918b67b 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -94,6 +94,11 @@ def test_gets_utf_16
     assert_equal("line2\n".encode("utf-16le"), stringio.gets)
     assert_equal("line3\n".encode("utf-16le"), stringio.gets)
     assert_nil(stringio.gets)
+    stringio.rewind
+    assert_equal("line1\n".encode("utf-16le"), stringio.gets("\n"))
+    assert_equal("line2\n".encode("utf-16le"), stringio.gets("\n"))
+    assert_equal("line3\n".encode("utf-16le"), stringio.gets("\n"))
+    assert_nil(stringio.gets)
   end
 
   def test_gets_chomp