diff --git a/clutter/clutter-stage.c b/clutter/clutter-stage.c
index 63f33d72a..6598b9c65 100644
--- a/clutter/clutter-stage.c
+++ b/clutter/clutter-stage.c
@@ -1668,6 +1668,16 @@ clutter_stage_set_use_fog (ClutterStage *stage,
  *   }
  * ]|
  *
+ * Note: The fogging functions only work correctly when the visible actors use
+ *       unmultiplied alpha colors. By default Cogl will premultiply textures
+ *       and cogl_set_source_color will premultiply colors, so unless you
+ *       explicitly load your textures requesting an unmultiplied
+ *       internal_format and use cogl_material_set_color you can only use
+ *       fogging with fully opaque actors.
+ *
+ *       We can look to improve this in the future when we can depend on
+ *       fragment shaders.
+ *
  * Since: 0.6
  */
 void
diff --git a/clutter/cogl/cogl.h.in b/clutter/cogl/cogl.h.in
index 64d57fc4f..26bcf25c2 100644
--- a/clutter/cogl/cogl.h.in
+++ b/clutter/cogl/cogl.h.in
@@ -386,13 +386,22 @@ gboolean        cogl_get_backface_culling_enabled (void);
  * @z_near: Position along z-axis where no fogging should be applied
  * @z_far: Position along z-axes where full fogging should be applied
  *
- * Enables fogging. Fogging causes vertices that are further away from
- * the eye to be rendered with a different color. The color is determined
- * according to the chosen fog mode; at it's simplest the color is
- * linearly interpolated so that vertices at @z_near are drawn fully
- * with their original color and vertices at @z_far are drawn fully
- * with @fog_color. Fogging will remain enabled until you call
- * cogl_disable_fog().
+ * Enables fogging. Fogging causes vertices that are further away from the eye
+ * to be rendered with a different color. The color is determined according to
+ * the chosen fog mode; at it's simplest the color is linearly interpolated so
+ * that vertices at @z_near are drawn fully with their original color and
+ * vertices at @z_far are drawn fully with @fog_color. Fogging will remain
+ * enabled until you call cogl_disable_fog().
+ *
+ * Note: The fogging functions only work correctly when primitives use
+ *       unmultiplied alpha colors. By default Cogl will premultiply textures
+ *       and cogl_set_source_color will premultiply colors, so unless you
+ *       explicitly load your textures requesting an unmultiplied
+ *       internal_format and use cogl_material_set_color you can only use
+ *       fogging with fully opaque primitives.
+ *
+ *       We can look to improve this in the future when we can depend on
+ *       fragment shaders.
  */
 void            cogl_set_fog                  (const CoglColor *fog_color,
                                                CoglFogMode      mode,
diff --git a/tests/interactive/test-depth.c b/tests/interactive/test-depth.c
index 7f5d1edd0..c06337c58 100644
--- a/tests/interactive/test-depth.c
+++ b/tests/interactive/test-depth.c
@@ -119,15 +119,12 @@ test_depth_main (int argc, char *argv[])
   ClutterActor     *group, *hand, *label, *rect, *janus, *box;
   ClutterColor      stage_color = { 0xcc, 0xcc, 0xcc, 0xff };
   ClutterColor      rect_color  = { 0, 0, 0, 0x88 };
-  ClutterFog        stage_fog   = { 10.0, -50.0 };
   GError           *error;
 
   clutter_init (&argc, &argv);
 
   stage = clutter_stage_get_default ();
   clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
-  clutter_stage_set_fog (CLUTTER_STAGE (stage), &stage_fog);
-  clutter_stage_set_use_fog (CLUTTER_STAGE (stage), TRUE);
 
   g_signal_connect (stage,
                     "button-press-event", G_CALLBACK (clutter_main_quit),