diff --git a/libavfilter/vf_idet.c b/libavfilter/vf_idet.c
index cd8bbe3567..70aae92228 100644
--- a/libavfilter/vf_idet.c
+++ b/libavfilter/vf_idet.c
@@ -118,8 +118,8 @@ static void filter(AVFilterContext *ctx)
         int refs = idet->cur->linesize[i];
 
         if (i && i<3) {
-            w >>= idet->csp->log2_chroma_w;
-            h >>= idet->csp->log2_chroma_h;
+            w = FF_CEIL_RSHIFT(w, idet->csp->log2_chroma_w);
+            h = FF_CEIL_RSHIFT(h, idet->csp->log2_chroma_h);
         }
 
         for (y = 2; y < h - 2; y++) {