diff --git a/os/vfs/drivers/overlay/drvoverlay.c b/os/vfs/drivers/overlay/drvoverlay.c
index a453f5c4c..bc1484913 100644
--- a/os/vfs/drivers/overlay/drvoverlay.c
+++ b/os/vfs/drivers/overlay/drvoverlay.c
@@ -119,7 +119,7 @@ static msg_t build_path(vfs_overlay_driver_c *drvp,
                         const char *path,
                         char *buf) {
 
-  *buf++ = '\0';
+  *buf = '\0';
 
   /* Copying the prefix, if defined.*/
   if (drvp->path_prefix != NULL) {