diff --git a/libavcodec/h264.h b/libavcodec/h264.h
index 7565e031d5..b1921ef6f6 100644
--- a/libavcodec/h264.h
+++ b/libavcodec/h264.h
@@ -409,7 +409,8 @@ typedef struct H264SliceContext {
     int mb_xy;
     int resync_mb_x;
     int resync_mb_y;
-    int mb_index_end;
+    // index of the first MB of the next slice
+    int next_slice_idx;
     int mb_skip_run;
     int is_complex;
 
diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index aee188ac5f..675ce61267 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -2321,10 +2321,9 @@ static int decode_slice(struct AVCodecContext *avctx, void *arg)
         for (;;) {
             // START_TIMER
             int ret, eos;
-
-            if (sl->mb_x + sl->mb_y * h->mb_width >= sl->mb_index_end) {
-                av_log(h->avctx, AV_LOG_ERROR, "Slice overlaps next at %d\n",
-                       sl->mb_index_end);
+            if (sl->mb_x + sl->mb_y * h->mb_width >= sl->next_slice_idx) {
+                av_log(h->avctx, AV_LOG_ERROR, "Slice overlaps with next at %d\n",
+                       sl->next_slice_idx);
                 er_add_slice(sl, sl->resync_mb_x, sl->resync_mb_y, sl->mb_x,
                              sl->mb_y, ER_MB_ERROR);
                 return AVERROR_INVALIDDATA;
@@ -2394,9 +2393,9 @@ static int decode_slice(struct AVCodecContext *avctx, void *arg)
         for (;;) {
             int ret;
 
-            if (sl->mb_x + sl->mb_y * h->mb_width >= sl->mb_index_end) {
-                av_log(h->avctx, AV_LOG_ERROR, "Slice overlaps next at %d\n",
-                       sl->mb_index_end);
+            if (sl->mb_x + sl->mb_y * h->mb_width >= sl->next_slice_idx) {
+                av_log(h->avctx, AV_LOG_ERROR, "Slice overlaps with next at %d\n",
+                       sl->next_slice_idx);
                 er_add_slice(sl, sl->resync_mb_x, sl->resync_mb_y, sl->mb_x,
                              sl->mb_y, ER_MB_ERROR);
                 return AVERROR_INVALIDDATA;
@@ -2486,38 +2485,45 @@ int ff_h264_execute_decode_slices(H264Context *h, unsigned context_count)
 {
     AVCodecContext *const avctx = h->avctx;
     H264SliceContext *sl;
-    int i;
+    int i, j;
 
     av_assert0(context_count && h->slice_ctx[context_count - 1].mb_y < h->mb_height);
 
-    h->slice_ctx[0].mb_index_end = INT_MAX;
+    h->slice_ctx[0].next_slice_idx = INT_MAX;
 
     if (h->avctx->hwaccel ||
         h->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU)
         return 0;
     if (context_count == 1) {
-        int ret = decode_slice(avctx, &h->slice_ctx[0]);
+        int ret;
+
+        h->slice_ctx[0].next_slice_idx = h->mb_width * h->mb_height;
+
+        ret = decode_slice(avctx, &h->slice_ctx[0]);
         h->mb_y = h->slice_ctx[0].mb_y;
         return ret;
     } else {
-        int j, mb_index;
         av_assert0(context_count > 0);
         for (i = 0; i < context_count; i++) {
-            int mb_index_end = h->mb_width * h->mb_height;
+            int next_slice_idx = h->mb_width * h->mb_height;
+            int slice_idx;
+
             sl                 = &h->slice_ctx[i];
-            mb_index = sl->resync_mb_x + sl->resync_mb_y * h->mb_width;
             if (CONFIG_ERROR_RESILIENCE) {
                 sl->er.error_count = 0;
             }
+
+            /* make sure none of those slices overlap */
+            slice_idx = sl->mb_y * h->mb_width + sl->mb_x;
             for (j = 0; j < context_count; j++) {
                 H264SliceContext *sl2 = &h->slice_ctx[j];
-                int mb_index2 = sl2->resync_mb_x + sl2->resync_mb_y * h->mb_width;
+                int        slice_idx2 = sl2->mb_y * h->mb_width + sl2->mb_x;
 
-                if (i==j || mb_index > mb_index2)
+                if (i == j || slice_idx2 < slice_idx)
                     continue;
-                mb_index_end = FFMIN(mb_index_end, mb_index2);
+                next_slice_idx = FFMIN(next_slice_idx, slice_idx2);
             }
-            sl->mb_index_end = mb_index_end;
+            sl->next_slice_idx = next_slice_idx;
         }
 
         avctx->execute(avctx, decode_slice, h->slice_ctx,