Nullable object must have a value. Help

Hi All. I have a vb class with the following inside it:
  Public Property MaxNumOfPages() As Nullable(Of Integer)
        Get
            Return mMaxNumOfPages
        End Get
        Set(ByVal value As Nullable(Of Integer))
            mMaxNumOfPages = value
        End Set
    End Property
 
Now, on another page, where i create a new instance of this class, i set the properties.  I have the following code:
 If txtMaxNumPages.Text.Length > 0 Then
       class1.MaxNumOfPages = txtMaxNumPages.Text
                Else
 & ...