BMFont error

TypeLoadException: Could not load type 'BMFont' from assembly 'Assembly-CSharp-firstpass, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
System.Reflection.MonoMethodInfo.GetMethodInfo (IntPtr handle)
System.Reflection.MonoMethod.GetPseudoCustomAttributes ()
System.MonoCustomAttrs.GetPseudoCustomAttributes (ICustomAttributeProvider obj, System.Type attributeType)
System.MonoCustomAttrs.GetCustomAttributesBase (ICustomAttributeProvider obj, System.Type attributeType)
System.MonoCustomAttrs.GetCustomAttributes (ICustomAttributeProvider obj, System.Type attributeType, Boolean inherit)
System.Reflection.MonoMethod.GetCustomAttributes (System.Type attributeType, Boolean inherit)
UnityEditor.AttributeHelper.ExtractMenuCommands (System.Reflection.Assembly assembly)