diff --git a/kernel/trunk/blkdev/disk.inc b/kernel/trunk/blkdev/disk.inc
index 375ece2b51..03bccc899b 100644
--- a/kernel/trunk/blkdev/disk.inc
+++ b/kernel/trunk/blkdev/disk.inc
@@ -82,7 +82,7 @@ struct  DISKFUNC
         adjust_cache_size       dd ?
 ; The pointer to the function which returns the cache size for this device.
 ; Optional, may be NULL.
-; unsigned int adjust_cache_size(unsigned int suggested_size);
+; unsigned int adjust_cache_size(void* userdata, unsigned int suggested_size);
 ; Return value: 0 = disable cache, otherwise = used cache size in bytes.
 ends
 
diff --git a/kernel/trunk/docs/drivers_api.txt b/kernel/trunk/docs/drivers_api.txt
index 3df3ac97dd..a96f7ccfb5 100644
--- a/kernel/trunk/docs/drivers_api.txt
+++ b/kernel/trunk/docs/drivers_api.txt
@@ -61,7 +61,7 @@ struc DISKFUNC
 ; implement a software cache for read/write, since they are called from the
 ; kernel cache manager.
   .adjust_cache_size dd ?
-; unsigned int adjust_cache_size(unsigned int suggested_size);
+; unsigned int adjust_cache_size(void* userdata, unsigned int suggested_size);
 ; Optional.
 ; Returns the cache size for this device in bytes. 0 = disable cache.
 }