Roslyn, Inheritance chain breaks in GetDeclaredSymbol() with assembly reference

Question

Scenario is that,

ClassA in current Project

ClassB in AssemblyB

ClassC in AssemblyC

Class Heirarchy

ClassA:ClassB
{
}

ClassB:ClassC
{
}

And the analyzer Code,

var declaredSymbol = _semanticModel.GetDeclaredSymbol( type);
var baseType = declaredSymbol.BaseType;

while (baseType != null && baseType.Name != "Object")
{
  inheritanceCount++;
  baseType = baseType.BaseType;
}

When type is ClassA, it can detect ClassB as basetype and after that the chain breaks, for ClassB it can't find BaseType (which should be ClassC, residing in Assembly C)