diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CodeMirrorDemo.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CodeMirrorDemo.java
index 9dfa02c280..1daa7eab00 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CodeMirrorDemo.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/CodeMirrorDemo.java
@@ -232,6 +232,8 @@ public class CodeMirrorDemo extends Screen {
     cm.on("cursorActivity", updateActiveLine(cm));
     cm.on("scroll", doScroll(cm));
     // TODO: Prevent right click from updating the cursor.
+    cm.addKeyMap(KeyMap.create().on("'j'", moveCursorDown(cm, 1)));
+    cm.addKeyMap(KeyMap.create().on("'k'", moveCursorDown(cm, -1)));
     cm.addKeyMap(KeyMap.create().on("'u'", upToChange()));
     cm.addKeyMap(KeyMap.create().on("'o'", toggleOpenBox(cm)));
     cm.addKeyMap(KeyMap.create().on("Enter", toggleOpenBox(cm)));
@@ -239,9 +241,12 @@ public class CodeMirrorDemo extends Screen {
     if (Gerrit.isSignedIn()) {
       cm.addKeyMap(KeyMap.create().on("'c'", insertNewDraft(cm)));
     }
-    // TODO: Work on a better way for customizing keybindings.
-    for (String s : new String[]{"C", "O", "R", "U", "Ctrl-C", "Ctrl-F",
-        "Enter"}) {
+    /**
+     * TODO: Work on a better way for customizing keybindings and remove
+     * temporary navigation hacks.
+     */
+    for (String s : new String[]{"C", "J", "K", "O", "R", "U", "Ctrl-C",
+        "Ctrl-F", "Enter"}) {
       CodeMirror.disableUnwantedKey("vim", s);
     }
   }
@@ -746,6 +751,14 @@ public class CodeMirrorDemo extends Screen {
     };
   }
 
+  private Runnable moveCursorDown(final CodeMirror cm, final int numLines) {
+    return new Runnable() {
+      public void run() {
+        cm.moveCursorDown(numLines);
+      }
+    };
+  }
+
   private Runnable upToChange() {
     return new Runnable() {
       public void run() {
diff --git a/gerrit-gwtui/src/main/java/net/codemirror/lib/CodeMirror.java b/gerrit-gwtui/src/main/java/net/codemirror/lib/CodeMirror.java
index a1692eb588..d2c5d55945 100644
--- a/gerrit-gwtui/src/main/java/net/codemirror/lib/CodeMirror.java
+++ b/gerrit-gwtui/src/main/java/net/codemirror/lib/CodeMirror.java
@@ -233,12 +233,17 @@ public class CodeMirror extends JavaScriptObject {
     $wnd.CodeMirror.keyMap[category][name] = undefined;
   }-*/;
 
-  public static native void defineVimEx(String name, String prefix, Runnable thunk) /*-{
+  public static final native void defineVimEx(String name, String prefix,
+      Runnable thunk) /*-{
     $wnd.CodeMirror.Vim.defineEx(name, prefix, $entry(function() {
       thunk.@java.lang.Runnable::run()();
     }));
   }-*/;
 
+  public final native void moveCursorDown(int numLines) /*-{
+    this.moveV(numLines, "line");
+  }-*/;
+
   public final native Element getGutterElement() /*-{
     return this.getGutterElement();
   }-*/;