diff --git a/src/ALabel.cpp b/src/ALabel.cpp
index 00b37d74..70d17655 100644
--- a/src/ALabel.cpp
+++ b/src/ALabel.cpp
@@ -40,7 +40,7 @@ std::string waybar::ALabel::getIcon(uint16_t percentage, const std::string& alt)
 {
   auto format_icons = config_["format-icons"];
   if (format_icons.isObject()) {
-    if (!alt.empty() && format_icons[alt]) {
+    if (!alt.empty() && format_icons[alt].isString()) {
       format_icons = format_icons[alt];
     } else {
       format_icons = format_icons["default"];