diff --git a/tests/virpcimock.c b/tests/virpcimock.c
index 829d61cd3f..cfe91ba3ff 100644
--- a/tests/virpcimock.c
+++ b/tests/virpcimock.c
@@ -935,6 +935,11 @@ open(const char *path, int flags, ...)
 }
 
 
+/* in some cases this function may not be present in headers, so we need
+ * a declaration to silence the complier */
+int
+__open_2(const char *path, int flags);
+
 int
 __open_2(const char *path, int flags)
 {