Index: src/org/openstreetmap/josm/gui/help/HelpBrowser.java
===================================================================
--- src/org/openstreetmap/josm/gui/help/HelpBrowser.java	(revision 11042)
+++ src/org/openstreetmap/josm/gui/help/HelpBrowser.java	(working copy)
@@ -15,6 +15,7 @@
 import java.awt.event.WindowEvent;
 import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.StringReader;
 import java.nio.charset.StandardCharsets;
@@ -49,6 +50,7 @@
 import org.openstreetmap.josm.gui.MainMenu;
 import org.openstreetmap.josm.gui.widgets.JosmEditorPane;
 import org.openstreetmap.josm.gui.widgets.JosmHTMLEditorKit;
+import org.openstreetmap.josm.io.CachedFile;
 import org.openstreetmap.josm.tools.ImageProvider;
 import org.openstreetmap.josm.tools.InputMapUtils;
 import org.openstreetmap.josm.tools.LanguageInfo.LocaleType;
@@ -139,11 +141,12 @@
     protected StyleSheet buildStyleSheet() {
         StyleSheet ss = new StyleSheet();
         StringBuilder css = new StringBuilder();
-        try (BufferedReader breader = new BufferedReader(
-                new InputStreamReader(
-                        getClass().getResourceAsStream("/data/help-browser.css"), StandardCharsets.UTF_8
-                )
-        )) {
+        try (CachedFile cf = new CachedFile("resource://data/help-browser.css");
+             InputStream cssStream = cf.getInputStream();
+             BufferedReader breader = new BufferedReader(
+                 new InputStreamReader(cssStream, StandardCharsets.UTF_8)
+             )
+        ) {
             String line;
             while ((line = breader.readLine()) != null) {
                 css.append(line);