diff --git a/apps/spkac.c b/apps/spkac.c
index f69dc5c..f3ee7e3 100644
--- a/apps/spkac.c
+++ b/apps/spkac.c
@@ -63,6 +63,7 @@
 #include <time.h>
 #include "apps.h"
 #include <openssl/bio.h>
+#include <openssl/conf.h>
 #include <openssl/err.h>
 #include <openssl/evp.h>
 #include <openssl/lhash.h>