diff --git a/apache2/msc_crypt.c b/apache2/msc_crypt.c
index d1d810fa..5699c832 100644
--- a/apache2/msc_crypt.c
+++ b/apache2/msc_crypt.c
@@ -16,6 +16,7 @@
 #include "msc_util.h"
 #include "apr_sha1.h"
 #include "apr_uri.h"
+#include "apr_base64.h"
 #include "acmp.h"
 #include "libxml/HTMLtree.h"
 #include "libxml/uri.h"