diff --git a/src/video/SDL_blit_slow.c b/src/video/SDL_blit_slow.c
index 45e6479a9..8702c7793 100644
--- a/src/video/SDL_blit_slow.c
+++ b/src/video/SDL_blit_slow.c
@@ -81,7 +81,7 @@ SDL_Blit_Slow(SDL_BlitInfo * info)
             }
             if (flags & SDL_COPY_COLORKEY) {
                 /* srcpixel isn't set for 24 bpp */
-                if (srcbpp == 24) {
+                if (srcbpp == 3) {
                     srcpixel = (srcR << src_fmt->Rshift) |
                         (srcG << src_fmt->Gshift) | (srcB << src_fmt->Bshift);
                 }