diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/Themer.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/Themer.java
index 82216688a4..a532209fbf 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/Themer.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/Themer.java
@@ -45,13 +45,17 @@ public class Themer {
   }
 
   public void set(ThemeInfo theme) {
-    set(theme.css() != null ? theme.css() : cssText,
-        theme.header() != null ? theme.header() : headerHtml,
-        theme.footer() != null ? theme.footer() : footerHtml);
+    if (theme != null) {
+      set(theme.css() != null ? theme.css() : cssText,
+          theme.header() != null ? theme.header() : headerHtml,
+          theme.footer() != null ? theme.footer() : footerHtml);
+    } else {
+      set(cssText, headerHtml, footerHtml);
+    }
   }
 
   public void clear() {
-    set(cssText, headerHtml, footerHtml);
+    set(null);
   }
 
   void init(Element css, Element header, Element footer) {
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/Screen.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/Screen.java
index ccc6a56d6d..a26db05e5b 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/Screen.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/Screen.java
@@ -62,7 +62,7 @@ public abstract class Screen extends View {
   protected void onUnload() {
     super.onUnload();
     if (setTheme) {
-      Gerrit.THEMER.set(null);
+      Gerrit.THEMER.clear();
     }
   }