diff --git a/editor/libeditor/text/nsPlaintextEditor.cpp b/editor/libeditor/text/nsPlaintextEditor.cpp
index feacf1694b9d..7dbd2e386e5e 100644
--- a/editor/libeditor/text/nsPlaintextEditor.cpp
+++ b/editor/libeditor/text/nsPlaintextEditor.cpp
@@ -527,6 +527,7 @@ NS_IMETHODIMP nsPlaintextEditor::HandleKeyPress(nsIDOMKeyEvent* aKeyEvent)
     
     if (character && !altKey && !ctrlKey && !isShift && !metaKey)
     {
+      aKeyEvent->PreventDefault();
       nsAutoString key(character);
       return TypedText(key, eTypedText);
     }