diff --git a/av1/av1_cx_iface.c b/av1/av1_cx_iface.c
index a11ee9c..93e8c24 100644
--- a/av1/av1_cx_iface.c
+++ b/av1/av1_cx_iface.c
@@ -538,7 +538,7 @@
   return (int)a;
 }
 
-void av1_reduce_ratio(aom_rational64_t *ratio) {
+static void reduce_ratio(aom_rational64_t *ratio) {
   const int denom = gcd(ratio->num, ratio->den);
   ratio->num /= denom;
   ratio->den /= denom;
@@ -2567,7 +2567,7 @@
       priv->timestamp_ratio.den = priv->cfg.g_timebase.den;
       priv->timestamp_ratio.num =
           (int64_t)priv->cfg.g_timebase.num * TICKS_PER_SEC;
-      av1_reduce_ratio(&priv->timestamp_ratio);
+      reduce_ratio(&priv->timestamp_ratio);
 
       set_encoder_config(&priv->oxcf, &priv->cfg, &priv->extra_cfg);
       if (priv->oxcf.rc_cfg.mode != AOM_CBR &&
diff --git a/av1/av1_cx_iface.h b/av1/av1_cx_iface.h
index f47fedd..05f4901 100644
--- a/av1/av1_cx_iface.h
+++ b/av1/av1_cx_iface.h
@@ -39,10 +39,6 @@
 
 int av1_get_image_bps(const aom_image_t *img);
 
-void av1_reduce_ratio(aom_rational64_t *ratio);
-
-int av1_gcd(int64_t a, int b);
-
 #ifdef __cplusplus
 }  // extern "C"
 #endif