diff --git a/libs/qsynedit/qsynedit/document.cpp b/libs/qsynedit/qsynedit/document.cpp
index 7fc59c34..ef08e905 100644
--- a/libs/qsynedit/qsynedit/document.cpp
+++ b/libs/qsynedit/qsynedit/document.cpp
@@ -1580,11 +1580,6 @@ size_t UndoItem::changeNumber() const
     return mChangeNumber;
 }
 
-unsigned int UndoItem::memoryUsage() const
-{
-    return mMemoryUsage;
-}
-
 UndoItem::UndoItem(ChangeReason reason, SelectionMode selMode,
                                  BufferCoord startPos, BufferCoord endPos,
                                  const QStringList& text, int number)
@@ -1599,9 +1594,6 @@ UndoItem::UndoItem(ChangeReason reason, SelectionMode selMode,
     foreach (const QString& s, text) {
         length+=s.length();
     }
-    mMemoryUsage =  length * sizeof(QChar) + text.length() * sizeof(QString)
-            + sizeof(UndoItem);
-//    qDebug()<<mMemoryUsage;
 }
 
 ChangeReason UndoItem::changeReason() const
diff --git a/libs/qsynedit/qsynedit/document.h b/libs/qsynedit/qsynedit/document.h
index 605c3fc0..f838cefb 100644
--- a/libs/qsynedit/qsynedit/document.h
+++ b/libs/qsynedit/qsynedit/document.h
@@ -656,7 +656,6 @@ private:
     BufferCoord mChangeEndPos;
     QStringList mChangeText;
     size_t mChangeNumber;
-    unsigned int mMemoryUsage;
 public:
     UndoItem(ChangeReason reason,
         SelectionMode selMode,
@@ -671,7 +670,6 @@ public:
     BufferCoord changeEndPos() const;
     QStringList changeText() const;
     size_t changeNumber() const;
-    unsigned int memoryUsage() const;
 };
 
 using PUndoItem = std::shared_ptr<UndoItem>;