diff --git a/dlls/wined3d/surface.c b/dlls/wined3d/surface.c
index e5f34f08f4c..a8e0f5190e9 100644
--- a/dlls/wined3d/surface.c
+++ b/dlls/wined3d/surface.c
@@ -3282,14 +3282,33 @@ static void convert_b8g8r8x8_unorm_b8g8r8a8_unorm_color_key(const BYTE *src, uns
     }
 }
 
+static void convert_b8g8r8a8_unorm_b8g8r8a8_unorm_color_key(const BYTE *src, unsigned int src_pitch,
+        BYTE *dst, unsigned int dst_pitch, unsigned int width, unsigned int height,
+        const struct wined3d_color_key *color_key)
+{
+    const DWORD *src_row;
+    unsigned int x, y;
+    DWORD *dst_row;
+
+    for (y = 0; y < height; ++y)
+    {
+        src_row = (DWORD *)&src[src_pitch * y];
+        dst_row = (DWORD *)&dst[dst_pitch * y];
+        for (x = 0; x < width; ++x)
+        {
+            DWORD src_color = src_row[x];
+            if (color_in_range(color_key, src_color))
+                src_color &= ~0xff000000;
+            dst_row[x] = src_color;
+        }
+    }
+}
+
 static HRESULT d3dfmt_convert_surface(const BYTE *src, BYTE *dst, UINT pitch, UINT width, UINT height,
         UINT outpitch, enum wined3d_conversion_type conversion_type, struct wined3d_surface *surface)
 {
     struct wined3d_palette *palette = NULL;
     struct wined3d_texture *texture;
-    const BYTE *source;
-    unsigned int x, y;
-    BYTE *dest;
 
     TRACE("src %p, dst %p, pitch %u, width %u, height %u, outpitch %u, conversion_type %#x, surface %p.\n",
             src, dst, pitch, width, height, outpitch, conversion_type, surface);
@@ -3325,20 +3344,8 @@ static HRESULT d3dfmt_convert_surface(const BYTE *src, BYTE *dst, UINT pitch, UI
             break;
 
         case WINED3D_CT_CK_B8G8R8A8:
-            for (y = 0; y < height; ++y)
-            {
-                source = src + pitch * y;
-                dest = dst + outpitch * y;
-                for (x = 0; x < width; ++x)
-                {
-                    DWORD color = *(const DWORD *)source;
-                    if (color_in_range(&texture->src_blt_color_key, color))
-                        color &= ~0xff000000;
-                    *(DWORD*)dest = color;
-                    source += 4;
-                    dest += 4;
-                }
-            }
+            convert_b8g8r8a8_unorm_b8g8r8a8_unorm_color_key(src, pitch, dst, outpitch,
+                    width, height, &texture->src_blt_color_key);
             break;
 
         default: