diff --git a/fpga_architecture.xsd b/fpga_architecture.xsd
index 0f844ea..fdb086c 100644
--- a/fpga_architecture.xsd
+++ b/fpga_architecture.xsd
@@ -272,6 +272,7 @@
     <xs:attribute name="name" type="xs:string" use="required"/>
     <xs:attribute name="R" type="xs:double" use="required"/>
     <xs:attribute name="Cin" type="xs:double" use="required"/>
+    <xs:attribute name="Cinternal" type="xs:double"/>
     <xs:attribute name="Cout" type="xs:double"/>
     <xs:attribute name="Tdel" type="xs:double"/>
     <xs:attribute name="buf_size" type="buf_size" default="auto"/>
diff --git a/routing_resource.xsd b/routing_resource.xsd
index c297460..8b9f4c0 100644
--- a/routing_resource.xsd
+++ b/routing_resource.xsd
@@ -38,6 +38,7 @@
   <xs:complexType name="timing">
     <xs:attribute name="R" type="xs:double"/>
     <xs:attribute name="Cin" type="xs:double"/>
+    <xs:attribute name="Cinternal" type="xs:double"/>
     <xs:attribute name="Cout" type="xs:double"/>
     <xs:attribute name="Tdel" type="xs:double"/>
   </xs:complexType>