--- a/devtools/client/jsonview/components/headers.js
+++ b/devtools/client/jsonview/components/headers.js
@@ -29,29 +29,25 @@ define(function(require, exports, module
 
     render: function() {
       let data = this.props.data;
 
       return (
         div({className: "netInfoHeadersTable"},
           div({className: "netHeadersGroup"},
             div({className: "netInfoHeadersGroup"},
-              span({className: "netHeader twisty"},
-                Locale.$STR("jsonViewer.responseHeaders")
-              )
+              Locale.$STR("jsonViewer.responseHeaders")
             ),
             table({cellPadding: 0, cellSpacing: 0},
               HeaderList({headers: data.response})
             )
           ),
           div({className: "netHeadersGroup"},
             div({className: "netInfoHeadersGroup"},
-              span({className: "netHeader twisty"},
-                Locale.$STR("jsonViewer.requestHeaders")
-              )
+              Locale.$STR("jsonViewer.requestHeaders")
             ),
             table({cellPadding: 0, cellSpacing: 0},
               HeaderList({headers: data.request})
             )
           )
         )
       );
     }

--- a/devtools/client/jsonview/css/headers-panel.css
+++ b/devtools/client/jsonview/css/headers-panel.css
@@ -25,29 +25,16 @@
 .headersPanelBox .netInfoHeadersGroup {
   margin-bottom: 10px;
   border-bottom: 1px solid #D7D7D7;
   padding-top: 8px;
   padding-bottom: 4px;
   font-family: Lucida Grande, Tahoma, sans-serif;
   font-weight: bold;
   color: #565656;
-}
-
-.headersPanelBox .netHeader.twisty {
-  background-image: url(twisty-open.svg);
-  background-repeat: no-repeat;
-  min-height: 12px;
-  background-position: 2px 50%;
-}
-
-.headersPanelBox .netHeader {
-  cursor: pointer;
-  padding-left: 17px;
-  position: static;
   -moz-user-select: none;
 }
 
 .headersPanelBox .netInfoParamValue code {
   display: block;
   color: #18191A;
   font-size: 11px;
   word-wrap: break-word;

--- a/devtools/client/jsonview/css/moz.build
+++ b/devtools/client/jsonview/css/moz.build
@@ -12,12 +12,10 @@ DevToolsModules(
     'headers-panel.css',
     'json-panel.css',
     'main.css',
     'read-only-prop.svg',
     'search-box.css',
     'search.svg',
     'tabs.css',
     'text-panel.css',
-    'toolbar.css',
-    'twisty-closed.svg',
-    'twisty-open.svg'
+    'toolbar.css'
 )

deleted file mode 100644
--- a/devtools/client/jsonview/css/twisty-closed.svg
+++ /dev/null
@@ -1,14 +0,0 @@
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-<svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" xmlns:xlink="http://www.w3.org/1999/xlink">
-  <defs>
-    <linearGradient id="a">
-      <stop offset="0" stop-color="#c3baaa"/>
-      <stop offset="1" stop-color="#fff"/>
-    </linearGradient>
-    <linearGradient id="b" x1="6.053" x2="2.888" y1="7.093" y2="1.8" xlink:href="#a" gradientUnits="userSpaceOnUse" gradientTransform="translate(.9 .9)"/>
-  </defs>
-  <rect width="8" height="8" x="1.5" y="1.5" fill="url(#b)" stroke="#7898b5" rx="1" ry="1" stroke-linecap="round" stroke-linejoin="round"/>
-  <path d="M5 3v2H3v1h2v2h1V6h2V5H6V3H5z"/>
-</svg>

deleted file mode 100644
--- a/devtools/client/jsonview/css/twisty-open.svg
+++ /dev/null
@@ -1,14 +0,0 @@
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-<svg xmlns="http://www.w3.org/2000/svg" width="11" height="11" xmlns:xlink="http://www.w3.org/1999/xlink">
-  <defs>
-    <linearGradient id="a">
-      <stop offset="0" stop-color="#c3baaa"/>
-      <stop offset="1" stop-color="#fff"/>
-    </linearGradient>
-    <linearGradient id="b" x1="6.053" x2="2.888" y1="7.093" y2="1.8" xlink:href="#a" gradientUnits="userSpaceOnUse" gradientTransform="translate(.9 .9)"/>
-  </defs>
-  <rect width="8" height="8" x="1.5" y="1.5" fill="url(#b)" stroke="#7898b5" rx="1" ry="1" stroke-linecap="round" stroke-linejoin="round"/>
-  <path d="M3 5h5v1H3z"/>
-</svg>