diff --git a/meta/recipes-extended/mailx/mailx_12.5.bb b/meta/recipes-extended/mailx/mailx_12.5.bb
index 080d71f150..a53da3af5d 100644
--- a/meta/recipes-extended/mailx/mailx_12.5.bb
+++ b/meta/recipes-extended/mailx/mailx_12.5.bb
@@ -29,3 +29,8 @@ inherit autotools-brokensep
 CFLAGS_append = " -D_BSD_SOURCE -DDEBIAN -I${S}/EXT"
 EXTRA_OEMAKE = "SENDMAIL=${sbindir}/sendmail"
 
+# The makeconfig can't run parallelly, otherwise the checking results
+# might be incorrect and lead to errors:
+# fio.c:56:17: fatal error: ssl.h: No such file or directory
+# #include <ssl.h>
+PARALLEL_MAKE = ""