diff --git a/src/core/nvo.c b/src/core/nvo.c
index 11074e67..5383fe5c 100644
--- a/src/core/nvo.c
+++ b/src/core/nvo.c
@@ -192,8 +192,8 @@ static int nvo_save ( struct nvo_block *nvo ) {
  * @v setting		Setting
  * @ret applies		Setting applies within this settings block
  */
-static int nvo_applies ( struct settings *settings __unused,
-			 struct setting *setting ) {
+int nvo_applies ( struct settings *settings __unused,
+		  struct setting *setting ) {
 
 	return dhcpopt_applies ( setting->tag );
 }
diff --git a/src/include/ipxe/nvo.h b/src/include/ipxe/nvo.h
index 36f41505..487f8b3f 100644
--- a/src/include/ipxe/nvo.h
+++ b/src/include/ipxe/nvo.h
@@ -45,6 +45,7 @@ struct nvo_block {
 /** Name of non-volatile options settings block */
 #define NVO_SETTINGS_NAME "nvo"
 
+extern int nvo_applies ( struct settings *settings, struct setting *setting );
 extern void nvo_init ( struct nvo_block *nvo, struct nvs_device *nvs,
 		       size_t address, size_t len,
 		       int ( * resize ) ( struct nvo_block *nvo, size_t len ),