diff --git a/test/src/mbgl/test/util.cpp b/test/src/mbgl/test/util.cpp
index ad726e60274..79de8bd4447 100644
--- a/test/src/mbgl/test/util.cpp
+++ b/test/src/mbgl/test/util.cpp
@@ -22,12 +22,12 @@ void checkImage(const std::string& base,
                 const PremultipliedImage& actual,
                 double imageThreshold,
                 double pixelThreshold) {
-//#if !TEST_READ_ONLY
-    //if (getenv("UPDATE")) {
+#if !TEST_READ_ONLY
+    if (getenv("UPDATE")) {
         util::write_file(base + "/expected.png", encodePNG(actual));
-        //return;
-    //}
-//#endif
+        return;
+    }
+#endif
 
     std::string expected_image;
     try {