diff --git a/ryu/ofproto/ofproto_v1_2.py b/ryu/ofproto/ofproto_v1_2.py
index 652bb100..e2db2a42 100644
--- a/ryu/ofproto/ofproto_v1_2.py
+++ b/ryu/ofproto/ofproto_v1_2.py
@@ -742,9 +742,9 @@ OFPRRFC_BAD_ROLE = 2        # Invalid role.
 
 # struct ofp_error_experimenter_msg
 OFP_ERROR_EXPERIMENTER_MSG_PACK_STR = '!HHI'
-OFP_ERROR_EXPERIMENTER_SIZE = 16
+OFP_ERROR_EXPERIMENTER_MSG_SIZE = 16
 assert (calcsize(OFP_ERROR_EXPERIMENTER_MSG_PACK_STR) + OFP_HEADER_SIZE ==
-        OFP_ERROR_EXPERIMENTER_SIZE)
+        OFP_ERROR_EXPERIMENTER_MSG_SIZE)
 
 # struct ofp_experimenter_header
 OFP_EXPERIMENTER_HEADER_PACK_STR = '!II'
diff --git a/ryu/ofproto/ofproto_v1_2_parser.py b/ryu/ofproto/ofproto_v1_2_parser.py
index 97ab485c..002be89c 100644
--- a/ryu/ofproto/ofproto_v1_2_parser.py
+++ b/ryu/ofproto/ofproto_v1_2_parser.py
@@ -162,7 +162,7 @@ class OFPErrorExperimenterMsg(MsgBase):
         msg.type, msg.exp_type, msg.experimenter = struct.unpack_from(
             ofproto_v1_2.OFP_ERROR_EXPERIMENTER_MSG_PACK_STR, msg.buf,
             ofproto_v1_2.OFP_HEADER_SIZE)
-        msg.data = msg.buf[ofproto_v1_2.OFP_ERROR_EXPERIMENTER_SIZE:]
+        msg.data = msg.buf[ofproto_v1_2.OFP_ERROR_EXPERIMENTER_MSG_SIZE:]
         return msg
 
 
diff --git a/ryu/tests/unit/ofproto/test_ofproto_v12.py b/ryu/tests/unit/ofproto/test_ofproto_v12.py
index 1d7551f3..556961b7 100644
--- a/ryu/tests/unit/ofproto/test_ofproto_v12.py
+++ b/ryu/tests/unit/ofproto/test_ofproto_v12.py
@@ -639,7 +639,7 @@ class TestOfprot12(unittest.TestCase):
 
     def test_struct_ofp_error_experimenter_msg(self):
         eq_(OFP_ERROR_EXPERIMENTER_MSG_PACK_STR, '!HHI')
-        eq_(OFP_ERROR_EXPERIMENTER_SIZE, 16)
+        eq_(OFP_ERROR_EXPERIMENTER_MSG_SIZE, 16)
 
     def test_struct_ofp_experimenter_header(self):
         eq_(OFP_EXPERIMENTER_HEADER_PACK_STR, '!II')