diff --git a/lib/hx509/hx509.h b/lib/hx509/hx509.h
index 3954b54b1..781f4a59c 100644
--- a/lib/hx509/hx509.h
+++ b/lib/hx509/hx509.h
@@ -39,6 +39,7 @@
 #include <rfc2459_asn1.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <heimbase.h>
 
 typedef struct hx509_cert_attribute_data *hx509_cert_attribute;
 typedef struct hx509_cert_data *hx509_cert;