diff --git a/src/app/commands/cmd_cel_properties.cpp b/src/app/commands/cmd_cel_properties.cpp
index f24a4371b..1cf2254f4 100644
--- a/src/app/commands/cmd_cel_properties.cpp
+++ b/src/app/commands/cmd_cel_properties.cpp
@@ -1,5 +1,5 @@
 /* Aseprite
- * Copyright (C) 2001-2013  David Capello
+ * Copyright (C) 2001-2014  David Capello
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -112,9 +112,16 @@ void CelPropertiesCommand::onExecute(Context* context)
     if (layer->isBackground()) {
       slider_opacity->setEnabled(false);
       tooltipManager->addTooltipFor(slider_opacity,
-                                    "The `Background' layer is opaque,\n"
-                                    "you can't change its opacity.",
-                                    JI_LEFT);
+        "The `Background' layer is opaque,\n"
+        "its opacity can't be changed.",
+        JI_LEFT);
+    }
+    else if (sprite->pixelFormat() == IMAGE_INDEXED) {
+      slider_opacity->setEnabled(false);
+      tooltipManager->addTooltipFor(slider_opacity,
+        "Cel opacity of Indexed images\n"
+        "cannot be changed.",
+        JI_LEFT);
     }
   }
   else {
diff --git a/src/app/document_api.cpp b/src/app/document_api.cpp
index 3e8cc2c36..0ceef39da 100644
--- a/src/app/document_api.cpp
+++ b/src/app/document_api.cpp
@@ -1,5 +1,5 @@
 /* Aseprite
- * Copyright (C) 2001-2013  David Capello
+ * Copyright (C) 2001-2014  David Capello
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -195,6 +195,17 @@ void DocumentApi::setPixelFormat(Sprite* sprite, PixelFormat newFormat, Ditherin
     replaceStockImage(sprite, c, new_image);
   }
 
+  // Set all cels opacity to 100% if we are converting to indexed.
+  if (newFormat == IMAGE_INDEXED) {
+    CelList cels;
+    sprite->getCels(cels);
+    for (CelIterator it = cels.begin(), end = cels.end(); it != end; ++it) {
+      Cel* cel = *it;
+      if (cel->opacity() < 255)
+        setCelOpacity(sprite, *it, 255);
+    }
+  }
+
   // Change sprite's pixel format.
   if (undoEnabled())
     m_undoers->pushUndoer(new undoers::SetSpritePixelFormat(getObjects(), sprite));
@@ -576,6 +587,7 @@ void DocumentApi::setCelPosition(Sprite* sprite, Cel* cel, int x, int y)
 void DocumentApi::setCelOpacity(Sprite* sprite, Cel* cel, int newOpacity)
 {
   ASSERT(cel);
+  ASSERT(sprite->supportAlpha());
 
   if (undoEnabled())
     m_undoers->pushUndoer(new undoers::SetCelOpacity(getObjects(), cel));
diff --git a/src/app/ui/status_bar.cpp b/src/app/ui/status_bar.cpp
index a77defafe..5f98a2a76 100644
--- a/src/app/ui/status_bar.cpp
+++ b/src/app/ui/status_bar.cpp
@@ -1,5 +1,5 @@
 /* Aseprite
- * Copyright (C) 2001-2013  David Capello
+ * Copyright (C) 2001-2014  David Capello
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -432,8 +432,10 @@ bool StatusBar::onProcessMessage(Message* msg)
       updateSubwidgetsVisibility();
 
       const Document* document = UIContext::instance()->activeDocument();
-      if (document != NULL)
+      if (document != NULL) {
+        updateFromLayer();
         updateCurrentFrame();
+      }
       break;
     }
 
@@ -610,7 +612,9 @@ void StatusBar::updateFromLayer()
     const Cel* cel;
 
     // Opacity layer
-    if (reader.layer() &&
+    if (reader.sprite() &&
+        reader.sprite()->supportAlpha() &&
+        reader.layer() &&
         reader.layer()->isImage() &&
         !reader.layer()->isBackground() &&
         (cel = reader.cel())) {
diff --git a/src/raster/sprite.cpp b/src/raster/sprite.cpp
index 47a83ffec..6c1551a87 100644
--- a/src/raster/sprite.cpp
+++ b/src/raster/sprite.cpp
@@ -174,6 +174,16 @@ bool Sprite::needAlpha() const
   return false;
 }
 
+bool Sprite::supportAlpha() const
+{
+  switch (m_format) {
+    case IMAGE_RGB:
+    case IMAGE_GRAYSCALE:
+      return true;
+  }
+  return false;
+}
+
 void Sprite::setTransparentColor(color_t color)
 {
   m_transparentColor = color;
diff --git a/src/raster/sprite.h b/src/raster/sprite.h
index f6ce134c2..e537554be 100644
--- a/src/raster/sprite.h
+++ b/src/raster/sprite.h
@@ -71,6 +71,7 @@ namespace raster {
     // than 255. Only RGBA and Grayscale images without background needs
     // alpha channel in the render.
     bool needAlpha() const;
+    bool supportAlpha() const;
 
     color_t transparentColor() const { return m_transparentColor; }
     void setTransparentColor(color_t color);