diff --git a/src/AgConfigure.cpp b/src/AgConfigure.cpp
index 32a1d21..5425355 100644
--- a/src/AgConfigure.cpp
+++ b/src/AgConfigure.cpp
@@ -540,7 +540,7 @@ String Configuration::toString(void) {
 
   /** "pmStandard" */
   if (config.inUSAQI) {
-    root["pmStandard"] = "USAQI";
+    root["pmStandard"] = "us-aqi";
   } else {
     root["pmStandard"] = "ugm3";
   }