diff --git a/dlls/winedos/int21.c b/dlls/winedos/int21.c
index 488bad8ad7cdab16c704e31723f389484f38f0df..e56d892f14fb47c5d84ea2789f7eabf86d0f55a5 100644
--- a/dlls/winedos/int21.c
+++ b/dlls/winedos/int21.c
@@ -3167,7 +3167,7 @@ static int INT21_GetFreeDiskSpace( CONTEXT86 *context )
     DWORD cluster_sectors, sector_bytes, free_clusters, total_clusters;
     WCHAR root[] = {'A',':','\\',0};
 
-    root[0] += INT21_MapDrive(BL_reg(context));
+    root[0] += INT21_MapDrive(DL_reg(context));
     if (!GetDiskFreeSpaceW( root, &cluster_sectors, &sector_bytes,
                             &free_clusters, &total_clusters )) return 0;
     SET_AX( context, cluster_sectors );