diff --git a/src/display/annotation_layer.js b/src/display/annotation_layer.js
index 8c3212fa4..ef3c106d3 100644
--- a/src/display/annotation_layer.js
+++ b/src/display/annotation_layer.js
@@ -14,8 +14,8 @@
  */
 
 import {
-  addLinkAttributes, CustomStyle, DOMSVGFactory, getDefaultSetting,
-  getFilenameFromUrl, LinkTarget
+  addLinkAttributes, DOMSVGFactory, getDefaultSetting, getFilenameFromUrl,
+  LinkTarget
 } from './dom_utils';
 import {
   AnnotationBorderStyleType, AnnotationType, stringToPDFString, unreachable,
@@ -153,10 +153,8 @@ class AnnotationElement {
       page.view[3] - data.rect[3] + page.view[1]
     ]);
 
-    CustomStyle.setProp('transform', container,
-                        'matrix(' + viewport.transform.join(',') + ')');
-    CustomStyle.setProp('transformOrigin', container,
-                        -rect[0] + 'px ' + -rect[1] + 'px');
+    container.style.transform = 'matrix(' + viewport.transform.join(',') + ')';
+    container.style.transformOrigin = -rect[0] + 'px ' + -rect[1] + 'px';
 
     if (!ignoreBorder && data.borderStyle.width > 0) {
       container.style.borderWidth = data.borderStyle.width + 'px';
@@ -172,7 +170,7 @@ class AnnotationElement {
       let verticalRadius = data.borderStyle.verticalCornerRadius;
       if (horizontalRadius > 0 || verticalRadius > 0) {
         let radius = horizontalRadius + 'px / ' + verticalRadius + 'px';
-        CustomStyle.setProp('borderRadius', container, radius);
+        container.style.borderRadius = radius;
       }
 
       switch (data.borderStyle.style) {
@@ -652,9 +650,8 @@ class PopupAnnotationElement extends AnnotationElement {
     // PDF viewers ignore a popup annotation's rectangle.
     let parentLeft = parseFloat(parentElement.style.left);
     let parentWidth = parseFloat(parentElement.style.width);
-    CustomStyle.setProp('transformOrigin', this.container,
-                        -(parentLeft + parentWidth) + 'px -' +
-                        parentElement.style.top);
+    this.container.style.transformOrigin =
+      -(parentLeft + parentWidth) + 'px -' + parentElement.style.top;
     this.container.style.left = (parentLeft + parentWidth) + 'px';
 
     this.container.appendChild(popup.render());
@@ -1235,8 +1232,8 @@ class AnnotationLayer {
       let element = parameters.div.querySelector(
         '[data-annotation-id="' + data.id + '"]');
       if (element) {
-        CustomStyle.setProp('transform', element,
-          'matrix(' + parameters.viewport.transform.join(',') + ')');
+        element.style.transform =
+          'matrix(' + parameters.viewport.transform.join(',') + ')';
       }
     }
     parameters.div.removeAttribute('hidden');
diff --git a/src/display/dom_utils.js b/src/display/dom_utils.js
index 894addde7..9c12d3c32 100644
--- a/src/display/dom_utils.js
+++ b/src/display/dom_utils.js
@@ -261,60 +261,6 @@ class SimpleXMLParser {
   }
 }
 
-/**
- * Optimised CSS custom property getter/setter.
- * @class
- */
-var CustomStyle = (function CustomStyleClosure() {
-
-  // As noted on: http://www.zachstronaut.com/posts/2009/02/17/
-  //              animate-css-transforms-firefox-webkit.html
-  // in some versions of IE9 it is critical that ms appear in this list
-  // before Moz
-  var prefixes = ['ms', 'Moz', 'Webkit', 'O'];
-  var _cache = Object.create(null);
-
-  function CustomStyle() {}
-
-  CustomStyle.getProp = function get(propName, element) {
-    // check cache only when no element is given
-    if (arguments.length === 1 && typeof _cache[propName] === 'string') {
-      return _cache[propName];
-    }
-
-    element = element || document.documentElement;
-    var style = element.style, prefixed, uPropName;
-
-    // test standard property first
-    if (typeof style[propName] === 'string') {
-      return (_cache[propName] = propName);
-    }
-
-    // capitalize
-    uPropName = propName.charAt(0).toUpperCase() + propName.slice(1);
-
-    // test vendor specific properties
-    for (var i = 0, l = prefixes.length; i < l; i++) {
-      prefixed = prefixes[i] + uPropName;
-      if (typeof style[prefixed] === 'string') {
-        return (_cache[propName] = prefixed);
-      }
-    }
-
-    // If all fails then set to undefined.
-    return (_cache[propName] = 'undefined');
-  };
-
-  CustomStyle.setProp = function set(propName, element, str) {
-    var prop = this.getProp(propName);
-    if (prop !== 'undefined') {
-      element.style[prop] = str;
-    }
-  };
-
-  return CustomStyle;
-})();
-
 var RenderingCancelledException = (function RenderingCancelledException() {
   function RenderingCancelledException(msg, type) {
     this.message = msg;
@@ -543,7 +489,6 @@ class DummyStatTimer {
 }
 
 export {
-  CustomStyle,
   RenderingCancelledException,
   addLinkAttributes,
   isExternalLinkTargetSet,
diff --git a/src/display/global.js b/src/display/global.js
index a09b7be1a..885781cd6 100644
--- a/src/display/global.js
+++ b/src/display/global.js
@@ -14,7 +14,7 @@
  */
 
 import {
-  addLinkAttributes, CustomStyle, DEFAULT_LINK_REL, getFilenameFromUrl,
+  addLinkAttributes, DEFAULT_LINK_REL, getFilenameFromUrl,
   isExternalLinkTargetSet, isValidUrl, LinkTarget
 } from './dom_utils';
 import {
@@ -243,7 +243,6 @@ PDFJS.LoopbackPort = LoopbackPort;
 PDFJS.PDFDataRangeTransport = PDFDataRangeTransport;
 PDFJS.PDFWorker = PDFWorker;
 
-PDFJS.CustomStyle = CustomStyle;
 PDFJS.LinkTarget = LinkTarget;
 PDFJS.addLinkAttributes = addLinkAttributes;
 PDFJS.getFilenameFromUrl = getFilenameFromUrl;
diff --git a/src/display/text_layer.js b/src/display/text_layer.js
index ddd9b6917..4362fa7b4 100644
--- a/src/display/text_layer.js
+++ b/src/display/text_layer.js
@@ -14,7 +14,7 @@
  */
 
 import { AbortException, createPromiseCapability, Util } from '../shared/util';
-import { CustomStyle, getDefaultSetting } from './dom_utils';
+import { getDefaultSetting } from './dom_utils';
 
 /**
  * Text layer render parameters.
@@ -547,7 +547,7 @@ var renderTextLayer = (function renderTextLayerClosure() {
       }
       if (transform !== '') {
         textDivProperties.originalTransform = transform;
-        CustomStyle.setProp('transform', textDiv, transform);
+        textDiv.style.transform = transform;
       }
       this._textDivProperties.set(textDiv, textDivProperties);
       textLayerFrag.appendChild(textDiv);
@@ -653,12 +653,11 @@ var renderTextLayer = (function renderTextLayerClosure() {
             div.setAttribute('style', divProperties.style + padding);
           }
           if (transform !== '') {
-            CustomStyle.setProp('transform', div, transform);
+            div.style.transform = transform;
           }
         } else {
           div.style.padding = 0;
-          CustomStyle.setProp('transform', div,
-                              divProperties.originalTransform || '');
+          div.style.transform = divProperties.originalTransform || '';
         }
       }
     },
diff --git a/src/pdf.js b/src/pdf.js
index 2f8728ae7..0d7ed0ca3 100644
--- a/src/pdf.js
+++ b/src/pdf.js
@@ -53,7 +53,6 @@ exports.PDFDataRangeTransport = pdfjsDisplayAPI.PDFDataRangeTransport;
 exports.PDFWorker = pdfjsDisplayAPI.PDFWorker;
 exports.renderTextLayer = pdfjsDisplayTextLayer.renderTextLayer;
 exports.AnnotationLayer = pdfjsDisplayAnnotationLayer.AnnotationLayer;
-exports.CustomStyle = pdfjsDisplayDOMUtils.CustomStyle;
 exports.createPromiseCapability = pdfjsSharedUtil.createPromiseCapability;
 exports.PasswordResponses = pdfjsSharedUtil.PasswordResponses;
 exports.InvalidPDFException = pdfjsSharedUtil.InvalidPDFException;
diff --git a/web/pdf_page_view.js b/web/pdf_page_view.js
index 18c4cf848..50e1ac1a3 100644
--- a/web/pdf_page_view.js
+++ b/web/pdf_page_view.js
@@ -18,8 +18,7 @@ import {
   RendererType, roundToDivide
 } from './ui_utils';
 import {
-  createPromiseCapability, CustomStyle, PDFJS, RenderingCancelledException,
-  SVGGraphics
+  createPromiseCapability, PDFJS, RenderingCancelledException, SVGGraphics
 } from 'pdfjs-lib';
 import { getGlobalEventBus } from './dom_events';
 import { RenderingStates } from './pdf_rendering_queue';
@@ -280,7 +279,7 @@ class PDFPageView {
     }
     let cssTransform = 'rotate(' + relativeRotation + 'deg) ' +
       'scale(' + scaleX + ',' + scaleY + ')';
-    CustomStyle.setProp('transform', target, cssTransform);
+    target.style.transform = cssTransform;
 
     if (this.textLayer) {
       // Rotating the text layer is more complicated since the divs inside the
@@ -317,11 +316,12 @@ class PDFPageView {
           console.error('Bad rotation value.');
           break;
       }
-      CustomStyle.setProp('transform', textLayerDiv,
-          'rotate(' + textAbsRotation + 'deg) ' +
-          'scale(' + scale + ', ' + scale + ') ' +
-          'translate(' + transX + ', ' + transY + ')');
-      CustomStyle.setProp('transformOrigin', textLayerDiv, '0% 0%');
+
+      textLayerDiv.style.transform =
+        'rotate(' + textAbsRotation + 'deg) ' +
+        'scale(' + scale + ', ' + scale + ') ' +
+        'translate(' + transX + ', ' + transY + ')';
+      textLayerDiv.style.transformOrigin = '0% 0%';
     }
 
     if (redrawAnnotations && this.annotationLayer) {