diff --git a/ChangeLog b/ChangeLog
index ac834ad..1aaf7ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,7 @@ ChangeLog
 - 0.27.0
 
   - remove unittest2 requirements for python 2.6 (#156)
+  - fixed subprotocol case during header validation (#158)
   - refactoring.
 
 - 0.26.0
diff --git a/websocket/_handshake.py b/websocket/_handshake.py
index 10b6ec9..ddcd4d3 100644
--- a/websocket/_handshake.py
+++ b/websocket/_handshake.py
@@ -117,8 +117,8 @@ def _validate(headers, key, subprotocols):
             return False, None
 
     if subprotocols:
-        subproto = headers.get("sec-websocket-protocol", None)
-        if not subproto or subproto not in subprotocols:
+        subproto = headers.get("sec-websocket-protocol", None).lower()
+        if not subproto or subproto not in [s.lower() for s in subprotocols]:
             error("Invalid subprotocol: " + str(subprotocols))
             return False, None
 
diff --git a/websocket/tests/test_websocket.py b/websocket/tests/test_websocket.py
index ab2a881..983ccf1 100644
--- a/websocket/tests/test_websocket.py
+++ b/websocket/tests/test_websocket.py
@@ -213,6 +213,11 @@ class WebSocketTest(unittest.TestCase):
         self.assertEqual(_validate_header(header, key, ["sub1", "sub2"]), (True, "sub1"))
         self.assertEqual(_validate_header(header, key, ["sub2", "sub3"]), (False, None))
 
+        header = required_header.copy()
+        header["sec-websocket-protocol"] = "sUb1"
+        self.assertEqual(_validate_header(header, key, ["Sub1", "suB2"]), (True, "sub1"))
+
+
     def testReadHeader(self):
         status, header = read_headers(HeaderSockMock("data/header01.txt"))
         self.assertEqual(status, 101)