diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index a8f5c85a9751e40219bf08e6b0ec2e1ca35833ca..791245d949984560d26bbd65f189b1c787e357b2 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -319,7 +319,7 @@ static void build_activity_map(VP9_COMP *cpi) {
 }
 
 // Macroblock activity masking
-void vp9_activity_masking(VP9_COMP *cpi, MACROBLOCK *x) {
+static void activity_masking(VP9_COMP *cpi, MACROBLOCK *x) {
 #if USE_ACT_INDEX
   x->rdmult += *(x->mb_activity_ptr) * (x->rdmult >> 2);
   x->errorperbit = x->rdmult * 100 / (110 * x->rddiv);
@@ -673,7 +673,7 @@ static void rd_pick_sb_modes(VP9_COMP *cpi, const TileInfo *const tile,
   }
 
   if (cpi->oxcf.tuning == VP8_TUNE_SSIM)
-    vp9_activity_masking(cpi, x);
+    activity_masking(cpi, x);
 
   if (cpi->oxcf.aq_mode == VARIANCE_AQ) {
     vp9_clear_system_state();  // __asm emms;
diff --git a/vp9/encoder/vp9_onyx_int.h b/vp9/encoder/vp9_onyx_int.h
index 075229089331edd01006f152b5fb1eb13cade16c..90ed606f6670da82b07da9fcfa0fc6e808d848a9 100644
--- a/vp9/encoder/vp9_onyx_int.h
+++ b/vp9/encoder/vp9_onyx_int.h
@@ -692,8 +692,6 @@ void vp9_encode_frame(VP9_COMP *cpi);
 
 void vp9_pack_bitstream(VP9_COMP *cpi, uint8_t *dest, size_t *size);
 
-void vp9_activity_masking(VP9_COMP *cpi, MACROBLOCK *x);
-
 void vp9_set_speed_features(VP9_COMP *cpi);
 
 int vp9_calc_ss_err(const YV12_BUFFER_CONFIG *source,