diff --git a/src/app/file/gif_format.cpp b/src/app/file/gif_format.cpp
index 185c64bf1..0a1af26e9 100644
--- a/src/app/file/gif_format.cpp
+++ b/src/app/file/gif_format.cpp
@@ -1050,7 +1050,47 @@ public:
                                            m_fop->newBlend(),
                                            RgbMapAlgorithm::OCTREE, // TODO configurable?
                                            false); // Do not add the transparent color yet
+        m_transparentIndex = 0;
+        m_globalColormapPalette = newPalette;
+        m_globalColormap = createColorMap(&m_globalColormapPalette);
+      }
+    }
 
+    // The following "if" block is intended to address cases where
+    // the Color Mode of the animation is RGB and can be represented by
+    // an absolute palette because it contains fewer than 256 colors
+    // throughout the entire animation. In this way the memory space
+    // used to generate the GIF is much more efficient, since local
+    // palettes don't need to be inserted in each frame. It also
+    // fixes a display issue with GIF files (generated by
+    // Aseprite 1.3.13) on Discord when the GIF parameters were:
+    // - disposal = DO_NOT_DISPOSE = 1
+    // - Local palettes exist.
+    if (m_spec.colorMode() == ColorMode::RGB || m_spec.colorMode() == ColorMode::GRAYSCALE) {
+      Palette newPalette(0, 512);
+      render::create_palette_from_sprite(m_sprite,
+                                         0,
+                                         totalFrames() - 1,
+                                         false,
+                                         &newPalette,
+                                         nullptr,
+                                         m_fop->newBlend(),
+                                         RgbMapAlgorithm::OCTREE,
+                                         false); // No effect on OctreeMap.
+      // Case: palette with (256 colors + mask color) == 257 but
+      // the mask color isn't used in the sprite.
+      if (newPalette.size() == 257 && !m_sprite->isColorUsed(0)) {
+        // Forcing GIF with background
+        m_transparentIndex = -1;
+        m_hasBackground = true;
+        // Discard the mask color (palette entry = 0)
+        for (int i = 0; i < 256; i++)
+          newPalette.setEntry(i, newPalette.getEntry(i + 1));
+        newPalette.resize(256);
+        m_globalColormapPalette = newPalette;
+        m_globalColormap = createColorMap(&m_globalColormapPalette);
+      }
+      else if (newPalette.size() <= 256) {
         m_transparentIndex = 0;
         m_globalColormapPalette = newPalette;
         m_globalColormap = createColorMap(&m_globalColormapPalette);
@@ -1388,15 +1428,18 @@ private:
 
     if (!m_preservePaletteOrder) {
       const LockImageBits<RgbTraits> srcBits(m_deltaImage.get());
+      const LockImageBits<RgbTraits> preBits(m_previousImage, frameBounds);
       LockImageBits<IndexedTraits> dstBits(frameImage.get());
 
       auto srcIt = srcBits.begin();
       auto dstIt = dstBits.begin();
+      auto preIt = preBits.begin();
 
       for (int y = 0; y < frameBounds.h; ++y) {
-        for (int x = 0; x < frameBounds.w; ++x, ++srcIt, ++dstIt) {
+        for (int x = 0; x < frameBounds.w; ++x, ++srcIt, ++dstIt, ++preIt) {
           ASSERT(srcIt != srcBits.end());
           ASSERT(dstIt != dstBits.end());
+          ASSERT(preIt != preBits.end());
 
           color_t color = *srcIt;
           int i;
@@ -1410,9 +1453,19 @@ private:
             if (i < 0)
               i = octree.mapColor(color | rgba_a_mask); // alpha=255
           }
+          // If the alpha in a pixel from m_deltaImage is < 128, the
+          // pixel is assumed to be 0. Then it should draw the pixel
+          // according defined m_transparentIndex or disposal method
           else {
             if (m_transparentIndex >= 0)
               i = m_transparentIndex;
+            else if (disposal == DisposalMethod::DO_NOT_DISPOSE) {
+              i = framePalette.findExactMatch(rgba_getr(*preIt),
+                                              rgba_getg(*preIt),
+                                              rgba_getb(*preIt),
+                                              255,
+                                              -1);
+            }
             else
               i = m_bgIndex;
           }
diff --git a/src/doc/primitives.cpp b/src/doc/primitives.cpp
index be10329fe..c8df70f8c 100644
--- a/src/doc/primitives.cpp
+++ b/src/doc/primitives.cpp
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (c) 2018-2023 Igara Studio S.A.
+// Copyright (c) 2018-2025 Igara Studio S.A.
 // Copyright (c) 2001-2016 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -352,6 +352,18 @@ bool is_plain_image_templ(const Image* img, const color_t color)
   return true;
 }
 
+template<typename ImageTraits>
+bool is_color_used_templ(const Image* img, const doc::color_t color)
+{
+  const LockImageBits<ImageTraits> bits(img);
+  auto it = bits.begin(), end = bits.end();
+  for (; it != end; ++it) {
+    if (*it == color)
+      return true;
+  }
+  return false;
+}
+
 template<typename ImageTraits>
 int count_diff_between_images_templ(const Image* i1, const Image* i2)
 {
@@ -464,6 +476,16 @@ bool is_plain_image(const Image* img, color_t c)
   return false;
 }
 
+bool is_color_used(const Image* img, color_t c)
+{
+  ASSERT(img->pixelFormat() == IMAGE_RGB || img->pixelFormat() == IMAGE_GRAYSCALE);
+  switch (img->pixelFormat()) {
+    case IMAGE_RGB:       return is_color_used_templ<RgbTraits>(img, c);
+    case IMAGE_GRAYSCALE: return is_color_used_templ<GrayscaleTraits>(img, c);
+  }
+  return false;
+}
+
 bool is_empty_image(const Image* img)
 {
   color_t c = 0; // alpha = 0
diff --git a/src/doc/primitives.h b/src/doc/primitives.h
index f8348d704..f12323547 100644
--- a/src/doc/primitives.h
+++ b/src/doc/primitives.h
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (c) 2018-2023 Igara Studio S.A.
+// Copyright (c) 2018-2025 Igara Studio S.A.
 // Copyright (c) 2001-2016 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -65,6 +65,7 @@ void fill_ellipse(Image* image,
                   color_t color);
 
 bool is_plain_image(const Image* img, color_t c);
+bool is_color_used(const Image* img, color_t c);
 bool is_empty_image(const Image* img);
 
 int count_diff_between_images(const Image* i1, const Image* i2);
diff --git a/src/doc/sprite.cpp b/src/doc/sprite.cpp
index a698eb572..dea6f3574 100644
--- a/src/doc/sprite.cpp
+++ b/src/doc/sprite.cpp
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (C) 2018-2024  Igara Studio S.A.
+// Copyright (C) 2018-2025  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -223,6 +223,18 @@ bool Sprite::isOpaque() const
   return (bg && bg->isVisible());
 }
 
+bool Sprite::isColorUsed(const doc::color_t c) const
+{
+  ASSERT(pixelFormat() == IMAGE_RGB || pixelFormat() == IMAGE_GRAYSCALE);
+  for (Cel* cel : cels()) {
+    if (cel && cel->image()) {
+      if (is_color_used(cel->image(), c))
+        return true;
+    }
+  }
+  return false;
+}
+
 bool Sprite::needAlpha() const
 {
   switch (pixelFormat()) {
diff --git a/src/doc/sprite.h b/src/doc/sprite.h
index f4b6852f5..c2022cc68 100644
--- a/src/doc/sprite.h
+++ b/src/doc/sprite.h
@@ -110,6 +110,9 @@ public:
   // Returns true if the sprite has a background layer and it's visible
   bool isOpaque() const;
 
+  // Returns true if the sprite is using a pixel with color c
+  bool isColorUsed(const doc::color_t c) const;
+
   // Returns true if the rendered images will contain alpha values less
   // than 255. Only RGBA and Grayscale images without background needs
   // alpha channel in the render.