diff --git a/src/ssl/ngx_lua_kong_ssl.c b/src/ssl/ngx_lua_kong_ssl.c
index a16f7872..a9d3e295 100644
--- a/src/ssl/ngx_lua_kong_ssl.c
+++ b/src/ssl/ngx_lua_kong_ssl.c
@@ -251,6 +251,13 @@ ngx_lua_kong_ssl_set_upstream_ssl(ngx_lua_kong_ssl_ctx_t *ctx, ngx_connection_t
             goto failed;
         }
 
+        /* clear the old chain */
+        if (SSL_clear_chain_certs(sc) == 0) {
+            ngx_ssl_error(NGX_LOG_ALERT, c->log, 0,
+                          "SSL_clear_chain_certs() failed");
+            goto failed;            
+        }
+
         /* read rest of the chain */
 
         for (i = 1; i < sk_X509_num(chain); i++) {
diff --git a/t/002-upstream-tls.t b/t/002-upstream-tls.t
index c975b924..4ccea4b1 100644
--- a/t/002-upstream-tls.t
+++ b/t/002-upstream-tls.t
@@ -5,7 +5,7 @@ use Cwd qw(cwd);
 
 repeat_each(2);
 
-plan tests => repeat_each() * (blocks() * 6);
+plan tests => repeat_each() * (blocks() * 6 + 1);
 
 my $pwd = cwd();
 
@@ -810,3 +810,81 @@ X509_check_host(): match
 [error]
 [crit]
 [alert]
+
+
+
+=== TEST 14: set_upstream_client_cert_and_key should clear the old chain
+--- http_config
+    lua_package_path "../lua-resty-core/lib/?.lua;lualib/?.lua;;";
+
+    server {
+        listen unix:$TEST_NGINX_HTML_DIR/nginx.sock ssl;
+        server_name   example.com;
+        ssl_certificate ../../cert/example.com.crt;
+        ssl_certificate_key ../../cert/example.com.key;
+        ssl_client_certificate ../../cert/ca.crt;
+        ssl_verify_client on;
+
+        server_tokens off;
+
+        location /foo {
+            default_type 'text/plain';
+            more_clear_headers Date;
+            echo 'it works!';
+        }
+    }
+
+    upstream foo {
+        server unix:$TEST_NGINX_HTML_DIR/nginx.sock;
+
+        balancer_by_lua_block {
+            collectgarbage() -- to make leak check mode pass
+
+            local tls = require("resty.kong.tls")
+            local ssl = require("ngx.ssl")
+
+            local f = assert(io.open("t/cert/client_leaf.crt"))
+            local cert_data = f:read("*a")
+            f:close()
+
+            local chain = assert(ssl.parse_pem_cert(cert_data))
+
+            f = assert(io.open("t/cert/client_example.com.key"))
+            local key_data = f:read("*a")
+            f:close()
+
+            local key = assert(ssl.parse_pem_priv_key(key_data))
+
+            local ok, err = tls.set_upstream_cert_and_key(chain, key)
+            if not ok then
+                ngx.say("set_upstream_cert_and_key failed: ", err)
+            end
+        }
+    }
+--- config
+    server_tokens off;
+
+    location /t {
+        proxy_ssl_trusted_certificate ../../cert/ca.crt;
+        proxy_ssl_verify on;
+        proxy_ssl_name example.com;
+        proxy_ssl_certificate ../../cert/client_example.com.crt;
+        proxy_ssl_certificate_key ../../cert/client_example.com.key;
+        proxy_ssl_session_reuse off;
+        proxy_pass https://foo/foo;
+    }
+
+--- request
+GET /t
+--- response_body_like
+.+400 The SSL certificate error.+
+
+--- error_log
+verify:0, error:21, depth:0, subject:"/C=US/ST=California/O=Kong Testing/CN=foo@example.com", issuer:"/C=US/ST=California/O=Kong Testing/CN=Kong Testing Intermidiate CA"
+client SSL certificate verify error: (21:unable to verify the first certificate) while reading client request headers
+
+--- error_code: 400
+--- no_error_log
+[error]
+[crit]
+[alert]
diff --git a/t/cert/client_leaf.crt b/t/cert/client_leaf.crt
new file mode 100644
index 00000000..6fafa161
--- /dev/null
+++ b/t/cert/client_leaf.crt
@@ -0,0 +1,30 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----