diff --git a/lib/events.js b/lib/events.js
index 665b529..4519ea9 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -164,7 +164,7 @@ MapboxEventManager.prototype = {
       proximity = [geocoder.options.proximity.longitude, geocoder.options.proximity.latitude];
     } else if (geocoder.options.proximity === 'ip') {
       var ipProximityHeader = geocoder._headers ? geocoder._headers['ip-proximity'] : null;
-      if (ipProximityHeader) {
+      if (ipProximityHeader && typeof ipProximityHeader === 'string') {
         proximity = ipProximityHeader.split(',').map(parseFloat);
       } else {
         proximity = [999,999];  // Alias for 'ip' in event logs