diff --git a/core/siren-core-modules.el b/core/siren-core-modules.el
index 9174843..3c23488 100644
--- a/core/siren-core-modules.el
+++ b/core/siren-core-modules.el
@@ -213,6 +213,7 @@
 (require 'siren-typescript)
 (require 'siren-vue)
 (require 'siren-web-mode)
+(require 'siren-x509)
 (require 'siren-xml)
 (require 'siren-yaml)
 
diff --git a/modules/languages/siren-x509.el b/modules/languages/siren-x509.el
new file mode 100644
index 0000000..a153b6b
--- /dev/null
+++ b/modules/languages/siren-x509.el
@@ -0,0 +1,13 @@
+;;; siren-x509.el --- jimeh's Emacs Siren: x509-mode configuration.
+
+;;; Commentary:
+
+;; Basic configuration for x509-mode.
+
+;;; Code:
+
+(use-package x509-mode
+  :defer t)
+
+(provide 'siren-x509)
+;;; siren-x509.el ends here
diff --git a/straight/versions/default.el b/straight/versions/default.el
index 015fb98..1f660e9 100644
--- a/straight/versions/default.el
+++ b/straight/versions/default.el
@@ -227,6 +227,7 @@
  ("vundo" . "80f5cb5775bb4120e36b2959db07fc88993eff81")
  ("web-mode" . "d8258fb33cc1918a2d83ff637157061e804acd6f")
  ("with-editor" . "1d5860cfd05d6805018bd071b8f9b56493ba11c6")
+ ("x509-mode" . "0e34667fac01fe42f0d8a6e501b5bbd5d4982e8e")
  ("xref" . "feb30d284d45e4904501d65b515069a1e365e07a")
  ("xterm-color" . "1a4012854c69a5cdaeb5a73d2ad705011892fca3")
  ("xwwp" . "f67e070a6e1b233e60274deb717274b000923231")