diff --git a/codemirror/codemirror.d.ts b/codemirror/codemirror.d.ts
index cd067fac5..babaa57ec 100644
--- a/codemirror/codemirror.d.ts
+++ b/codemirror/codemirror.d.ts
@@ -793,7 +793,7 @@ declare module CodeMirror {
         clearOnEnter?: boolean;
 
         /** Determines whether the mark is automatically cleared when it becomes empty. Default is true. */
-        clearWhenEmpty: boolean;
+        clearWhenEmpty?: boolean;
         
         /** Use a given node to display this range.Implies both collapsed and atomic.
         The given DOM node must be an inline element(as opposed to a block element). */
@@ -803,7 +803,7 @@ declare module CodeMirror {
          * capture mouse and drag events occurring in this widget. Default is
          * false—the events will be left alone for the default browser handler,
          * or specific handlers on the widget, to capture. */
-        handleMouseEvents: boolean;
+        handleMouseEvents?: boolean;
         
         /** A read - only span can, as long as it is not cleared, not be modified except by calling setValue to reset the whole document.
         Note: adding a read - only span currently clears the undo history of the editor,
@@ -823,7 +823,7 @@ declare module CodeMirror {
         css?: string;
 
         /** When given, will give the nodes created for this span a HTML title attribute with the given value. */
-        title: string;
+        title?: string;
         
         /** When the target document is linked to other documents, you can set shared to true to make the marker appear in all documents.
         By default, a marker appears only in its target document. */