diff --git a/ChangeLog b/ChangeLog
index e184c9670..e3e77f2fb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,8 @@ Bugfix
    * Allow loading symlinked certificates. Fixes #3005. Reported and fixed
      by Jonathan Bennett <JBennett@incomsystems.biz> via #3008.
    * Fix an unchecked call to mbedtls_md() in the x509write module.
+   * 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
 
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6cf7781f2..51ae9da3c 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" ) );