diff --git a/tool/generate.go b/tool/generate.go
index 12730a2..b06adf4 100644
--- a/tool/generate.go
+++ b/tool/generate.go
@@ -83,6 +83,8 @@ func main() {
                         <tbody>`)
 
     for _, sourcePath := range os.Args[1:] {
+	    fmt.Fprint(os.Stderr, ".")
+
         lexer := whichLexer(sourcePath)
         lines := readLines(sourcePath)