diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index fc95c327445b33873eea1f958a60b977a7507834..f2a13de99a20b32f46a6933a127474a579296bd7 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -198,7 +198,7 @@ static void calc_av_activity(VP9_COMP *cpi, int64_t activity_sum) {
 #define OUTPUT_NORM_ACT_STATS   0
 
 #if USE_ACT_INDEX
-// Calculate and activity index for each mb
+// Calculate an activity index for each mb
 static void calc_activity_index(VP9_COMP *cpi, MACROBLOCK *x) {
   VP9_COMMON *const cm = &cpi->common;
   int mb_row, mb_col;
@@ -268,6 +268,8 @@ static void build_activity_map(VP9_COMP *cpi) {
   unsigned int mb_activity;
   int64_t activity_sum = 0;
 
+  x->mb_activity_ptr = cpi->mb_activity_map;
+
   // for each macroblock row in image
   for (mb_row = 0; mb_row < cm->mb_rows; mb_row++) {
 #if ALT_ACT_MEASURE