diff --git a/R/group_rows.R b/R/group_rows.R
index 7009995..7300eb3 100644
--- a/R/group_rows.R
+++ b/R/group_rows.R
@@ -34,7 +34,9 @@
 
   kable_format <- attr(kable_input, "format")
   if (!kable_format %in% c("html", "latex")) {
-    message("Currently generic markdown table using pandoc is not supported.")
+    warning("Please specify format in kable. kableExtra can customize either ",
+            "HTML or LaTeX outputs. See https://haozhu233.github.io/kableExtra/ ",
+            "for details.")
     return(kable_input)
   }
   if (is.null(index)) {