diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index 8953f0f..a6d059b 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -243,14 +243,16 @@
 static void duplicate_mode_info_in_sb(VP9_COMMON *cm, MACROBLOCKD *xd,
                                       int mi_row, int mi_col,
                                       BLOCK_SIZE bsize) {
-  const int block_width = num_8x8_blocks_wide_lookup[bsize];
-  const int block_height = num_8x8_blocks_high_lookup[bsize];
+  const int block_width = VPXMIN(num_8x8_blocks_wide_lookup[bsize],
+                                 cm->mi_cols - mi_col);
+  const int block_height = VPXMIN(num_8x8_blocks_high_lookup[bsize],
+                                  cm->mi_rows - mi_row);
+  const int mi_stride = xd->mi_stride;
+  MODE_INFO *const src_mi = xd->mi[0];
   int i, j;
   for (j = 0; j < block_height; ++j)
-    for (i = 0; i < block_width; ++i) {
-      if (mi_row + j < cm->mi_rows && mi_col + i < cm->mi_cols)
-        xd->mi[j * xd->mi_stride + i] = xd->mi[0];
-    }
+    for (i = 0; i < block_width; ++i)
+      xd->mi[j * mi_stride + i] = src_mi;
 }
 
 static void set_block_size(VP9_COMP * const cpi,