diff --git a/build-helpers/build-doom-profile.sh b/build-helpers/build-doom-profile.sh
index d4cf9b2..288034a 100644
--- a/build-helpers/build-doom-profile.sh
+++ b/build-helpers/build-doom-profile.sh
@@ -45,7 +45,8 @@ if [[ -n "$profileName" ]]; then
     export HOME=$(mktemp -d)
     export DOOMPROFILE="$profileName";
 fi
-$runtimeShell $doomSource/bin/doomscript $buildProfile
+$runtimeShell $doomSource/bin/doomscript $buildProfile \
+    -l $deps/share/emacs/site-lisp
 
 # Similar to audit-tmpdir.sh in nixpkgs.
 if grep -q -F "$TMPDIR/" -r $out; then
diff --git a/build-helpers/build-profile b/build-helpers/build-profile
index f41d99a..58d83e1 100755
--- a/build-helpers/build-profile
+++ b/build-helpers/build-profile
@@ -18,6 +18,21 @@
 ;; We skip Doom's normal install and initialization.
 (require 'straight)
 
+;; Set from run!
+(defvar site-lisp)
+
+(defun generate-nix-autoloads ()
+  "Pull in autoloads for non-ELPA emacsWithPackages dependencies."
+  (let (filenames)
+    (dolist (filename (directory-files site-lisp))
+      (when (string-suffix-p "-autoloads.el" filename)
+        (push (expand-file-name filename site-lisp) filenames)))
+    (doom-autoloads--scan filenames doom-autoloads-excluded-files 'literal)))
+
+(add-to-list
+ 'doom-profile-generators
+ '("80-loaddefs-nix.auto.el" . generate-nix-autoloads))
+
 ;; Doom runs this with package.el activated, but suppresses activation during
 ;; normal startup. Store the side effects of activation in the profile to avoid
 ;; (slow) package activation during normal startup.
@@ -54,7 +69,8 @@
 
 (add-to-list 'doom-autoloads-cached-vars 'package-activated-list)
 
-(defcli! build-profile ()
+(defcli! build-profile
+    ((site-lisp ("-l" dir) "site-lisp directory to load autoloads from"))
   "Write a Doom profile."
   ;; Load our generated profile's init.el. Both to get the profile right and to
   ;; load the advice to make Doom not install straight.
diff --git a/checks.nix b/checks.nix
index 63cab0b..47877c8 100644
--- a/checks.nix
+++ b/checks.nix
@@ -81,6 +81,8 @@ in {
   interactive-without-loader = doomTest "no-profile" { config.default = true; } { profileName = ""; };
   interactive-no-profile-hack = doomTest "no-profile" { config.default = true; } { noProfileHack = true; };
 
+  cmake = doomTest "cmake" { lang.cc = true; } { };
+
   org-re-reveal = doomTest "org-re-reveal" { lang.org = [ "+present" ]; } { };
 
   # Various tests of module combinations.
diff --git a/default.nix b/default.nix
index 168e048..54fed71 100644
--- a/default.nix
+++ b/default.nix
@@ -326,6 +326,7 @@ let
     buildProfile = ./build-helpers/build-profile;
     initEl = ./init.el;
     EMACS = lib.getExe emacsWithPackages;
+    inherit (emacsWithPackages) deps;
     # Enable this to troubleshoot failures at this step.
     #DEBUG = "1";
 
diff --git a/tests.el b/tests.el
index 56120fb..c445eab 100644
--- a/tests.el
+++ b/tests.el
@@ -41,6 +41,11 @@
   (unless (string-search "/site-lisp/revealjs" org-re-reveal-root)
     (error "org-re-reveal does not find our revealjs: %s" org-re-reveal-root)))
 
+(defun test-cmake ()
+  "Test cmake-mode autoloads are loaded."
+  (unless (functionp 'cmake-mode)
+    (error "cmake-mode not available")))
+
 (defun test-doom ()
   (let* ((out (getenv "out"))
          (test (intern-soft (format "test-%s" (getenv "testName"))))