diff --git a/lib/gssapi/gssapi/gssapi.h b/lib/gssapi/gssapi/gssapi.h
index 1c6501ba9..c634aea49 100644
--- a/lib/gssapi/gssapi/gssapi.h
+++ b/lib/gssapi/gssapi/gssapi.h
@@ -37,6 +37,7 @@
 /*
  * First, include stddef.h to get size_t defined.
  */
+#include <stdarg.h>
 #include <stddef.h>
 
 #include <krb5-types.h>