diff --git a/internal/util/common/url.go b/internal/util/common/url.go
index 13a71323b..c6cb2e4b8 100644
--- a/internal/util/common/url.go
+++ b/internal/util/common/url.go
@@ -16,9 +16,12 @@ func EnsureURLScheme(raw string) string {
 	if trimmed == "" {
 		return ""
 	}
+	// Schemes are case-insensitive (RFC 3986), and phone keyboards often
+	// capitalize the first letter ("Mailto:", "Tel:").
+	lower := strings.ToLower(trimmed)
 	if strings.Contains(trimmed, "://") ||
-		strings.HasPrefix(trimmed, "mailto:") ||
-		strings.HasPrefix(trimmed, "tel:") {
+		strings.HasPrefix(lower, "mailto:") ||
+		strings.HasPrefix(lower, "tel:") {
 		return trimmed
 	}
 	return "https://" + trimmed
diff --git a/internal/util/common/url_test.go b/internal/util/common/url_test.go
index 167ff6650..2d182294a 100644
--- a/internal/util/common/url_test.go
+++ b/internal/util/common/url_test.go
@@ -18,6 +18,8 @@ func TestEnsureURLScheme(t *testing.T) {
 		{"mailto", "mailto:support@example.com", "mailto:support@example.com"},
 		{"tel", "tel:+1234567890", "tel:+1234567890"},
 		{"trims whitespace", "  t.me/xui_support  ", "https://t.me/xui_support"},
+		{"capitalized mailto", "Mailto:support@example.com", "Mailto:support@example.com"},
+		{"uppercase tel", "TEL:+1234567890", "TEL:+1234567890"},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {