diff --git a/Makefile b/Makefile
index c72183e..6305363 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@
 RW_PB_EXT := build/yang/rw-pb-ext.yang
 Q?=@
 
-PYANG_OPTIONS := -Wnone
+PYANG_OPTIONS := -Werror
 
 all: $(PYTHON_MODELS) pyangbind
 	$(MAKE) package
diff --git a/models/yang/nsd.yang b/models/yang/nsd.yang
index dba3df4..48fc484 100644
--- a/models/yang/nsd.yang
+++ b/models/yang/nsd.yang
@@ -35,10 +35,6 @@
     prefix "inet";
   }
 
-  import ietf-yang-types {
-    prefix "yang";
-  }
-
   import mano-types {
     prefix "manotypes";
   }
diff --git a/models/yang/vnfd.yang b/models/yang/vnfd.yang
index 51bb9f7..b3f820d 100644
--- a/models/yang/vnfd.yang
+++ b/models/yang/vnfd.yang
@@ -27,14 +27,6 @@
     prefix "manotypes";
   }
 
-  import rw-pb-ext {
-    prefix "rwpb";
-  }
-
-  import ietf-yang-types {
-    prefix "yang";
-  }
-
   import ietf-inet-types {
     prefix "inet";
   }