diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index c01e2cb685ba..e9b7bf2c76ba 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -3612,6 +3612,7 @@ function mimeTypeIsTextBased(aMimeType)
          aMimeType.endsWith("+xml") ||
          aMimeType == "application/x-javascript" ||
          aMimeType == "application/javascript" ||
+         aMimeType == "application/json" ||
          aMimeType == "application/xml" ||
          aMimeType == "mozilla.application/cached-xul";
 }
diff --git a/toolkit/content/widgets/findbar.xml b/toolkit/content/widgets/findbar.xml
index e4c540fff39f..eea53d637fd7 100644
--- a/toolkit/content/widgets/findbar.xml
+++ b/toolkit/content/widgets/findbar.xml
@@ -1355,6 +1355,7 @@
           return /^text\/|\+xml$/.test(aMimeType) ||
                  aMimeType == "application/x-javascript" ||
                  aMimeType == "application/javascript" ||
+                 aMimeType == "application/json" ||
                  aMimeType == "application/xml";
         ]]></body>
       </method>