diff --git a/ChangeLog b/ChangeLog
index 79d9505b3..4eee33ddb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@ mbed TLS ChangeLog (Sorted per branch, date)
 = mbed TLS x.x.x branch released xxxx-xx-xx
 
 Bugfix
+<<<<<<< HEAD
    * Fix the redefinition of macro ssl_set_bio to an undefined symbol
      mbedtls_ssl_set_bio_timeout in compat-1.3.h, by removing it.
      Found by omlib-lin. #673
@@ -17,6 +18,8 @@ Bugfix
   * Fixed the templates used to generate project and solution files for Visual
      Studio 2015 as well as the files themselves, to remove a build warning
      generated in Visual Studio 2015. Reported by Steve Valliere. #742
+   * Fix a resource leak in ssl_cookie, when using MBEDTLS_THREADING_C.
+     Raised and fix suggested by Alan Gillingham in the mbed TLS forum. #771
 
 = mbed TLS 2.4.1 branch released 2016-12-13
 
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index 9fb32de7a..caf119990 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -98,7 +98,7 @@ void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
     mbedtls_md_free( &ctx->hmac_ctx );
 
 #if defined(MBEDTLS_THREADING_C)
-    mbedtls_mutex_init( &ctx->mutex );
+    mbedtls_mutex_free( &ctx->mutex );
 #endif
 
     mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );