diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 60c68198..e49a58c8 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -3,8 +3,9 @@ All notable changes to this project will be documented in this file.
 
 ## [5.1.6] - 2019-09-03
 
-Sending invalid UTF-8 TEXT message should fail and close the connection (fix remaining autobahn test: 6.X UTF-8 Handling)
-Fix failing unittest which was sending binary data in text mode with WebSocket::send to call properly call WebSocket::sendBinary instead.
+- Sending invalid UTF-8 TEXT message should fail and close the connection (fix remaining autobahn test: 6.X UTF-8 Handling)
+- Fix failing unittest which was sending binary data in text mode with WebSocket::send to call properly call WebSocket::sendBinary instead.
+- Validate that the reason is proper utf-8. (fix autobahn test 7.5.1)
 
 ## [5.1.5] - 2019-09-03
 
diff --git a/ixwebsocket/IXWebSocketTransport.cpp b/ixwebsocket/IXWebSocketTransport.cpp
index 20221cba..d5664dde 100644
--- a/ixwebsocket/IXWebSocketTransport.cpp
+++ b/ixwebsocket/IXWebSocketTransport.cpp
@@ -37,6 +37,7 @@
 #include "IXWebSocketHttpHeaders.h"
 #include "IXUrlParser.h"
 #include "IXSocketFactory.h"
+#include "IXUtf8Validator.h"
 
 #include <string.h>
 #include <stdlib.h>
@@ -676,6 +677,13 @@ namespace ix
                         reason.assign(_rxbuf.begin()+ws.header_size + 2,
                                       _rxbuf.begin()+ws.header_size + (size_t) ws.N);
                     }
+
+                    // Validate that the reason is proper utf-8. Autobahn 7.5.1
+                    if (!validateUtf8(reason))
+                    {
+                        code = WebSocketCloseConstants::kInvalidFramePayloadData;
+                        reason = WebSocketCloseConstants::kInvalidFramePayloadDataMessage;
+                    }
                 }
                 else
                 {