diff --git a/storage/myisam/mi_check.c b/storage/myisam/mi_check.c
index 917e142af91..c5995d74ca3 100644
--- a/storage/myisam/mi_check.c
+++ b/storage/myisam/mi_check.c
@@ -4791,8 +4791,7 @@ static int replace_data_file(HA_CHECK *param, MI_INFO *info, File new_file)
   */
   if (info->s->file_map)
   {
-    (void) my_munmap((char*) info->s->file_map,
-                     (size_t) info->s->mmaped_length);
+    (void) my_munmap((char*) info->s->file_map, info->s->mmaped_length);
     info->s->file_map= NULL;
   }
 
diff --git a/storage/myisam/mi_dynrec.c b/storage/myisam/mi_dynrec.c
index c4baca3d89f..cb49ded0c20 100644
--- a/storage/myisam/mi_dynrec.c
+++ b/storage/myisam/mi_dynrec.c
@@ -95,7 +95,7 @@ my_bool mi_dynmap_file(MI_INFO *info, my_off_t size)
 #if defined(HAVE_MADVISE)
   madvise((char*) info->s->file_map, size, MADV_RANDOM);
 #endif
-  info->s->mmaped_length= size;
+  info->s->mmaped_length= (size_t) size;
   info->s->file_read= mi_mmap_pread;
   info->s->file_write= mi_mmap_pwrite;
   DBUG_RETURN(0);
@@ -118,8 +118,7 @@ int mi_munmap_file(MI_INFO *info)
 {
   int ret;
   DBUG_ENTER("mi_unmap_file");
-  if ((ret= my_munmap((void*) info->s->file_map,
-                      (size_t) info->s->mmaped_length)))
+  if ((ret= my_munmap((void*) info->s->file_map, info->s->mmaped_length)))
     DBUG_RETURN(ret);
   info->s->file_read= mi_nommap_pread;
   info->s->file_write= mi_nommap_pwrite;
diff --git a/storage/myisam/mi_locking.c b/storage/myisam/mi_locking.c
index e61cd745936..4fd287c6038 100644
--- a/storage/myisam/mi_locking.c
+++ b/storage/myisam/mi_locking.c
@@ -114,7 +114,7 @@ int mi_lock_database(MI_INFO *info, int lock_type)
 	  if (myisam_flush)
 	  {
             if (share->file_map)
-              my_msync(info->dfile, share->file_map, (size_t)share->mmaped_length, MS_SYNC);
+              my_msync(info->dfile, share->file_map, share->mmaped_length, MS_SYNC);
             if (mysql_file_sync(share->kfile, MYF(0)))
 	      mark_crashed= error= my_errno;
             if (mysql_file_sync(info->dfile, MYF(0)))
@@ -529,7 +529,7 @@ int _mi_writeinfo(register MI_INFO *info, uint operation)
       if (myisam_flush)
       {
         if (share->file_map)
-          my_msync(info->dfile, share->file_map, (size_t)share->mmaped_length, MS_SYNC);
+          my_msync(info->dfile, share->file_map, share->mmaped_length, MS_SYNC);
         mysql_file_sync(share->kfile, 0);
         mysql_file_sync(info->dfile, 0);
       }
diff --git a/storage/myisam/mi_packrec.c b/storage/myisam/mi_packrec.c
index fc32bb7e518..242bc82bd16 100644
--- a/storage/myisam/mi_packrec.c
+++ b/storage/myisam/mi_packrec.c
@@ -1551,7 +1551,7 @@ void _mi_unmap_file(MI_INFO *info)
 {
   DBUG_ASSERT(info->s->options & HA_OPTION_COMPRESS_RECORD);
 
-  (void) my_munmap((char*) info->s->file_map, (size_t) info->s->mmaped_length);
+  (void) my_munmap((char*) info->s->file_map, info->s->mmaped_length);
 
   if (myisam_mmap_size != SIZE_T_MAX)
   {
diff --git a/storage/myisam/myisamdef.h b/storage/myisam/myisamdef.h
index ff12cb53dd9..c63baa13875 100644
--- a/storage/myisam/myisamdef.h
+++ b/storage/myisam/myisamdef.h
@@ -224,7 +224,7 @@ typedef struct st_mi_isam_share
   THR_LOCK lock;
   mysql_mutex_t intern_lock;            /* Locking for use with _locking */
   mysql_rwlock_t *key_root_lock;
-  my_off_t mmaped_length;
+  size_t mmaped_length;
   uint     nonmmaped_inserts;           /* counter of writing in non-mmaped
                                            area */
   mysql_rwlock_t mmap_lock;