diff --git a/lib/adapters/xhr.js b/lib/adapters/xhr.js
index 8612a77802..fe3b33a02a 100644
--- a/lib/adapters/xhr.js
+++ b/lib/adapters/xhr.js
@@ -205,7 +205,8 @@ module.exports = function xhrAdapter(config) {
       }
     }
 
-    if (!requestData) {
+    // false, 0 (zero number), and '' (empty string) are valid JSON values
+    if (!requestData && requestData !== false && requestData !== 0 && requestData !== '') {
       requestData = null;
     }