diff --git a/libavformat/asfcrypt.c b/libavformat/asfcrypt.c
index c77e37503e..ed68fb60ed 100644
--- a/libavformat/asfcrypt.c
+++ b/libavformat/asfcrypt.c
@@ -73,7 +73,7 @@ static void multiswap_invert_keys(uint32_t keys[12])
         keys[i] = inverse(keys[i]);
 }
 
-static uint32_t multiswap_step(const uint32_t keys[12], uint32_t v)
+static uint32_t multiswap_step(const uint32_t keys[6], uint32_t v)
 {
     int i;
     v *= keys[0];
@@ -85,7 +85,7 @@ static uint32_t multiswap_step(const uint32_t keys[12], uint32_t v)
     return v;
 }
 
-static uint32_t multiswap_inv_step(const uint32_t keys[12], uint32_t v)
+static uint32_t multiswap_inv_step(const uint32_t keys[6], uint32_t v)
 {
     int i;
     v -= keys[5];