--- a/src/adapters/sdl/platform.cpp
+++ b/src/adapters/sdl/platform.cpp
@@ -5,6 +5,7 @@
 #include "openlf2/detail/sdl/frame_upscaler.hpp"
 #include "openlf2/detail/sdl/haptics.hpp"
 #include "openlf2/detail/sdl/setup_screen.hpp"
+#include "openlf2/detail/sdl/sprite_alpha.hpp"
 #ifdef OPENLF2_HAS_WINDOW_ICON
 #include "window_icon.hpp" // generated from the SVG icon by tools/icons/make_icons.py
 #endif
@@ -667,7 +668,7 @@
 #endif
                 if (!loaded) return error();
                 std::unique_ptr<SDL_Surface, DestroySurface> surface(
-                    SDL_ConvertSurface(loaded.get(), png ? SDL_PIXELFORMAT_ARGB8888 : SDL_PIXELFORMAT_XRGB8888));
+                    detail::sprite_surface_with_alpha(loaded.get(), png, sprite.color_key));
                 if (!surface) return error();
                 if (surface->w <= 0 || surface->h <= 0 || surface->w > 8192 || surface->h > 8192) {
                     return fail(ErrorCode::limit, "image dimensions exceed limits");
@@ -680,13 +681,10 @@
                     textures_.clear();
                     texture_bytes_ = 0;
                 }
-                if (sprite.color_key &&
-                    !SDL_SetSurfaceColorKey(surface.get(), true, SDL_MapSurfaceRGB(surface.get(), 0, 0, 0))) {
-                    return error();
-                }
                 Texture texture(SDL_CreateTextureFromSurface(renderer_.get(), surface.get()));
                 // Sprites are always sampled without filtering; linear scaling happens on the finished frame.
-                if (!texture || !SDL_SetTextureScaleMode(texture.get(), SDL_SCALEMODE_NEAREST)) return error();
+                if (!texture || !detail::set_sprite_texture_blend(texture.get(), png, sprite.color_key)
+                    || !SDL_SetTextureScaleMode(texture.get(), SDL_SCALEMODE_NEAREST)) return error();
                 textures_.emplace(key, std::move(texture));
                 texture_bytes_ += texture_bytes;
             }
--- /dev/null
+++ b/include/openlf2/detail/sdl/sprite_alpha.hpp
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: MIT
+#pragma once
+#include <SDL3/SDL.h>
+
+namespace openlf2::detail {
+// BMP sprites use exact RGB black as their transparent key. Materialize alpha
+// before texture upload: an XRGB color key can otherwise depend on the backend.
+// PNG alpha is already authored and must be preserved, including opaque black.
+inline SDL_Surface* sprite_surface_with_alpha(SDL_Surface* loaded, bool png, bool color_key) {
+    SDL_Surface* surface = SDL_ConvertSurface(loaded,
+        png || color_key ? SDL_PIXELFORMAT_ARGB8888 : SDL_PIXELFORMAT_XRGB8888);
+    if (!surface) return nullptr;
+    if (color_key && !png) {
+        if (!SDL_LockSurface(surface)) {
+            SDL_DestroySurface(surface);
+            return nullptr;
+        }
+        for (int y = 0; y < surface->h; ++y) {
+            auto* row = reinterpret_cast<Uint32*>(static_cast<Uint8*>(surface->pixels)
+                + y * surface->pitch);
+            for (int x = 0; x < surface->w; ++x) {
+                const Uint32 rgb = row[x] & 0x00ffffffu;
+                row[x] = rgb == 0 ? 0u : rgb | 0xff000000u;
+            }
+        }
+        SDL_UnlockSurface(surface);
+    }
+    return surface;
+}
+
+inline bool set_sprite_texture_blend(SDL_Texture* texture, bool png, bool color_key) {
+    return SDL_SetTextureBlendMode(texture,
+        png || color_key ? SDL_BLENDMODE_BLEND : SDL_BLENDMODE_NONE);
+}
+} // namespace openlf2::detail