diff --git a/libavcodec/ffv1.c b/libavcodec/ffv1.c
index 93cec14244..5b52849400 100644
--- a/libavcodec/ffv1.c
+++ b/libavcodec/ffv1.c
@@ -115,12 +115,11 @@ av_cold int ff_ffv1_init_slices_state(FFV1Context *f)
 
 av_cold int ff_ffv1_init_slice_contexts(FFV1Context *f)
 {
-    int i;
+    int i, max_slice_count = f->num_h_slices * f->num_v_slices;
 
-    f->max_slice_count = f->num_h_slices * f->num_v_slices;
-    av_assert0(f->max_slice_count > 0);
+    av_assert0(max_slice_count > 0);
 
-    for (i = 0; i < f->max_slice_count; i++) {
+    for (i = 0; i < max_slice_count; i++) {
         int sx          = i % f->num_h_slices;
         int sy          = i / f->num_h_slices;
         int sxs         = f->avctx->width  *  sx      / f->num_h_slices;
@@ -152,6 +151,7 @@ av_cold int ff_ffv1_init_slice_contexts(FFV1Context *f)
             goto memfail;
         }
     }
+    f->max_slice_count = max_slice_count;
     return 0;
 
 memfail: