diff --git a/libswscale/utils.c b/libswscale/utils.c
index bc8d7627e2..c3154d82c1 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -2042,6 +2042,7 @@ static int context_init_threaded(SwsContext *c,
         if (!c->slice_ctx[i])
             return AVERROR(ENOMEM);
 
+        c->nb_slice_ctx++;
         c->slice_ctx[i]->parent = c;
 
         ret = av_opt_copy((void*)c->slice_ctx[i], (void*)c);
@@ -2054,8 +2055,6 @@ static int context_init_threaded(SwsContext *c,
         if (ret < 0)
             return ret;
 
-        c->nb_slice_ctx++;
-
         if (c->slice_ctx[i]->dither == SWS_DITHER_ED) {
             av_log(c, AV_LOG_VERBOSE,
                    "Error-diffusion dither is in use, scaling will be single-threaded.");