diff --git a/config.el b/config.el
index 979fc68..703efb8 100644
--- a/config.el
+++ b/config.el
@@ -352,6 +352,18 @@
 (use-package! duplicate-thing
   :bind (("M-C" . duplicate-thing)))
 
+;; Debugger.
+(use-package! gud
+  :defer t
+  :init
+  (setq-default
+   ;; Use gdb-many-windows by default.
+   gdb-many-windows t
+   ;; Display source file containing main.
+   gdb-show-main t)
+  :config
+  (setq gud-chdir-before-run nil))
+
 ;; P4 programming mode.
 (use-package! p4_16-mode
   :mode (("\\.p4\\'" . p4_16-mode)