diff --git a/internal/check/variables.go b/internal/check/variables.go
index d9c8a938..3bbb90a9 100755
--- a/internal/check/variables.go
+++ b/internal/check/variables.go
@@ -34,7 +34,7 @@ func title(s string, except *regexp2.Regexp, tc *titlecase.TitleConverter, thres
 	words := 0.0
 
 	ps := `[\p{N}\p{L}*]+[^\s]*`
-	if except != nil {
+	if except != nil && except.String() != "" {
 		ps = except.String() + "|" + ps
 	}
 	re := regexp2.MustCompileStd(ps)
diff --git a/testdata/fixtures/styles/demo/test.mdx b/testdata/fixtures/styles/demo/test.mdx
index 544e4f9e..e0223d74 100644
--- a/testdata/fixtures/styles/demo/test.mdx
+++ b/testdata/fixtures/styles/demo/test.mdx
@@ -4,7 +4,7 @@
 
 this is not a heading.
 
-## this is *another* heading!
+## this is _another_ heading!
 
 ## this is another heading!