string_add.patch

diff --git a/pfp/fields.py b/pfp/fields.py
index cf4ee31..77da4eb 100644
--- a/pfp/fields.py
+++ b/pfp/fields.py
@@ -1720,7 +1720,7 @@ class String(Field):
 		:returns: TODO
 
 		"""
-		if isinstance(other, String):
+		if isinstance(other, str):
 			self._pfp__value += other._pfp__value
 		else:
 			self._pfp__value += PYSTR(other)
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 0d5ca77..74b5726 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -80,6 +80,26 @@ class TestNumericFields(unittest.TestCase, utils.UtilsMixin):
 			""",
 			stdout="9894494448401390090"
 		)
+
+	# temp_char ends up being of class Bytes in python 3 - but not on python 2
+	# This test ensures we can handle adding both a String and byte together
+	def test_add_strings(self):
+		dom = self._test_parse_build(
+			"\x01\x02\x03\x04\x05",
+			"""
+                                local string temp_expected, temp_char;
+                                local int i;
+                                for(i = 0; i < 5; i++) {
+                                    SPrintf(temp_char, "%.2X", ReadUByte(FTell()+i));
+                                    temp_expected += temp_char;
+                                }
+                                Printf("%s", temp_expected);
+                        """,
+			"0102030405",
+			False,
+			False,
+			False
+		)
 	
 if __name__ == "__main__":
 	unittest.main()