diff --git a/util/test/demos/gl/gl_buffer_updates.cpp b/util/test/demos/gl/gl_buffer_updates.cpp
index 213c14955..2f7ddd915 100644
--- a/util/test/demos/gl/gl_buffer_updates.cpp
+++ b/util/test/demos/gl/gl_buffer_updates.cpp
@@ -55,7 +55,10 @@ layout(binding = 0, std140) uniform constsbuf
 
 void main()
 {
-	Color = col;
+  if(col == vec4(0.0, 1.0, 0.0, 1.0))
+    Color = col;
+  else
+    Color = vec4(1.0, 0.0, 0.0, 1.0);
 }
 
 )EOSHADER";