diff --git a/ChangeLog b/ChangeLog
index 1d39172216c5..58f0e72d5496 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS x.x.x branch released xxxx-xx-xx
+
+Bugfix
+   * Fix build failure with MBEDTLS_ZLIB_SUPPORT enabled. Reported by
+     Jack Lloyd in #2859. Fix submitted by jiblime in #2963.
+
 = mbed TLS 2.20.0 branch released 2020-01-15
 
 Bugfix
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6cf7781f2ac6..51ae9da3c69e 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1880,7 +1880,7 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
 
     /* Allocate compression buffer */
 #if defined(MBEDTLS_ZLIB_SUPPORT)
-    if( session->compression == MBEDTLS_SSL_COMPRESS_DEFLATE &&
+    if( ssl->session_negotiate->compression == MBEDTLS_SSL_COMPRESS_DEFLATE &&
         ssl->compress_buf == NULL )
     {
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "Allocating compression buffer" ) );