diff --git a/internal/export/idna/example_test.go b/internal/export/idna/example_test.go
index 6e31be9..6e6b872 100644
--- a/internal/export/idna/example_test.go
+++ b/internal/export/idna/example_test.go
@@ -49,6 +49,10 @@
 		idna.Transitional(true)) // Map ß -> ss
 	fmt.Println(p.ToASCII("*.faß.com"))
 
+	// Lookup for registration. Also does not allow '*'.
+	p = idna.New(idna.ValidateForRegistration())
+	fmt.Println(p.ToUnicode("*.faß.com"))
+
 	// Set up a profile maps for lookup, but allows wild cards.
 	p = idna.New(
 		idna.MapForLookup(),
@@ -58,6 +62,7 @@
 
 	// Output:
 	// *.xn--fa-hia.com <nil>
-	// *.fass.com idna: disallowed rune U+002E
+	// *.fass.com idna: disallowed rune U+002A
+	// *.faß.com idna: disallowed rune U+002A
 	// *.fass.com <nil>
 }
diff --git a/internal/export/idna/idna.go b/internal/export/idna/idna.go
index a3d9ad2..3184fbb 100644
--- a/internal/export/idna/idna.go
+++ b/internal/export/idna/idna.go
@@ -373,23 +373,20 @@
 	if !norm.NFC.IsNormalString(s) {
 		return s, &labelError{s, "V1"}
 	}
-	var err error
 	for i := 0; i < len(s); {
 		v, sz := trie.lookupString(s[i:])
-		i += sz
 		// Copy bytes not copied so far.
 		switch p.simplify(info(v).category()) {
 		// TODO: handle the NV8 defined in the Unicode idna data set to allow
 		// for strict conformance to IDNA2008.
 		case valid, deviation:
 		case disallowed, mapped, unknown, ignored:
-			if err == nil {
-				r, _ := utf8.DecodeRuneInString(s[i:])
-				err = runeError(r)
-			}
+			r, _ := utf8.DecodeRuneInString(s[i:])
+			return s, runeError(r)
 		}
+		i += sz
 	}
-	return s, err
+	return s, nil
 }
 
 func validateAndMap(p *Profile, s string) (string, error) {
@@ -408,7 +405,7 @@
 			continue
 		case disallowed:
 			if err == nil {
-				r, _ := utf8.DecodeRuneInString(s[i:])
+				r, _ := utf8.DecodeRuneInString(s[start:])
 				err = runeError(r)
 			}
 			continue