diff --git a/js/libtextsecure.js b/js/libtextsecure.js
index fa5d03ea0f..59af9145e6 100644
--- a/js/libtextsecure.js
+++ b/js/libtextsecure.js
@@ -37501,12 +37501,13 @@ var TextSecureServer = (function() {
         }
         window.nodeFetch(url, fetchOptions).then(function(response) {
           var resultPromise;
-          if (options.responseType === 'json') {
+          if (options.responseType === 'json'
+              && response.headers.get('Content-Type') === 'application/json') {
             resultPromise = response.json();
-          } else if (!options.responseType || options.responseType === 'text') {
-            resultPromise = response.text();
           } else if (options.responseType === 'arraybuffer') {
             resultPromise = response.buffer();
+          } else {
+            resultPromise = response.text();
           }
           return resultPromise.then(function(result) {
             if (options.responseType === 'arraybuffer') {
diff --git a/libtextsecure/api.js b/libtextsecure/api.js
index 0c20d84167..aa8ee2c039 100644
--- a/libtextsecure/api.js
+++ b/libtextsecure/api.js
@@ -64,12 +64,13 @@ var TextSecureServer = (function() {
         }
         window.nodeFetch(url, fetchOptions).then(function(response) {
           var resultPromise;
-          if (options.responseType === 'json') {
+          if (options.responseType === 'json'
+              && response.headers.get('Content-Type') === 'application/json') {
             resultPromise = response.json();
-          } else if (!options.responseType || options.responseType === 'text') {
-            resultPromise = response.text();
           } else if (options.responseType === 'arraybuffer') {
             resultPromise = response.buffer();
+          } else {
+            resultPromise = response.text();
           }
           return resultPromise.then(function(result) {
             if (options.responseType === 'arraybuffer') {