diff --git a/src/plot_api/plot_api.js b/src/plot_api/plot_api.js
index 6b00272b00a..d3224a9dd12 100644
--- a/src/plot_api/plot_api.js
+++ b/src/plot_api/plot_api.js
@@ -2641,6 +2641,7 @@ function diffConfig(oldConfig, newConfig) {
     var key;
 
     for(key in oldConfig) {
+        if(key.charAt(0) === '_') continue;
         var oldVal = oldConfig[key];
         var newVal = newConfig[key];
         if(oldVal !== newVal) {
diff --git a/test/jasmine/assets/mock_lists.js b/test/jasmine/assets/mock_lists.js
index 2b0a4e8f61f..7b6387ab140 100644
--- a/test/jasmine/assets/mock_lists.js
+++ b/test/jasmine/assets/mock_lists.js
@@ -9,7 +9,7 @@ var svgMockList = [
     ['17', require('@mocks/17.json')],
     ['21', require('@mocks/21.json')],
     ['22', require('@mocks/22.json')],
-    ['airfoil', require('@mocks/airfoil.json')],
+    ['airfoil', require('@mocks/airfoil.json')], // important to keep because it's the only mock with config options
     ['annotations-autorange', require('@mocks/annotations-autorange.json')],
     ['axes_enumerated_ticks', require('@mocks/axes_enumerated_ticks.json')],
     ['axes_visible-false', require('@mocks/axes_visible-false.json')],