diff --git a/lib/hx509/hx_locl.h b/lib/hx509/hx_locl.h
index 15b6f61ef..87ccb7b81 100644
--- a/lib/hx509/hx_locl.h
+++ b/lib/hx509/hx_locl.h
@@ -57,6 +57,7 @@
 #include <pkcs9_asn1.h>
 #include <pkcs12_asn1.h>
 #include <ocsp_asn1.h>
+#include <pkcs10_asn1.h>
 #include <asn1_err.h>
 
 #include <der.h>