diff --git a/mozilla/dom/src/base/nsBarProps.cpp b/mozilla/dom/src/base/nsBarProps.cpp
index b775f7f7166..cad138f8d39 100644
--- a/mozilla/dom/src/base/nsBarProps.cpp
+++ b/mozilla/dom/src/base/nsBarProps.cpp
@@ -106,7 +106,7 @@ NS_IMETHODIMP BarPropImpl::SetVisibleByFlag(PRBool aVisible,
       if(aVisible)
          chromeFlags |= aChromeFlag;
       else
-         chromeFlags |= ~aChromeFlag;
+         chromeFlags &= ~aChromeFlag;
       NS_ENSURE_SUCCESS(mBrowserChrome->SetChromeFlags(chromeFlags),
          NS_ERROR_FAILURE);
       return NS_OK;