diff --git a/NEWS b/NEWS
index 1409bfb..dc790b5 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,8 @@
   - Only try to commit when changes have been discovered in the file. By
     extension git-auto-commit-mode won't ask for a summary to a commit that it
     won't make.
+  - Add option to prevent new (untracked) files from being added to the git
+    repository automatically, =gac-automatically-add-new-files-p=.
 
 * v4.5.0
 
diff --git a/README.org b/README.org
index 4fd5782..fc6a6e7 100644
--- a/README.org
+++ b/README.org
@@ -76,6 +76,10 @@
        repository's ~HEAD~ to its default upstream. Setting up the
        upstream is the user's responsibility.
 
+  - =gac-automatically-add-new-files-p= ::
+    A boolean value indicating whether or not git-auto-commit-mode should add
+    new (untracked) files to the repository.
+
   - =gac-ask-for-summary-p= :: A boolean value indicating whether or not
        git-auto-commit-mode should ask the user for a commit message every time
        a commit is made. *Note*: Since the summary is asked for before the commit,
diff --git a/git-auto-commit-mode.el b/git-auto-commit-mode.el
index 4fc6315..0bfdd6f 100644
--- a/git-auto-commit-mode.el
+++ b/git-auto-commit-mode.el
@@ -50,6 +50,12 @@ If non-nil a git push will be executed after each commit."
   :risky t)
 (make-variable-buffer-local 'gac-automatically-push-p)
 
+(defcustom gac-automatically-add-new-files-p t
+  "Should new (untracked) files automatically be committed to the repo?"
+  :tag "Automatically add new files"
+  :group 'git-auto-commit-mode
+  :type 'boolean)
+
 (defcustom gac-ask-for-summary-p nil
   "Ask the user for a short summary each time a file is committed?"
   :tag "Ask for a summary on each commit"
@@ -185,7 +191,8 @@ should already have been set up."
 (defun gac--after-save (buffer)
   (unwind-protect
       (when (and (buffer-live-p buffer)
-                 (or (not (gac--buffer-is-tracked buffer))
+                 (or (and gac-automatically-add-new-files-p
+                          (not (gac--buffer-is-tracked buffer)))
                      (gac--buffer-has-changes buffer)))
         (gac-commit buffer)
         (with-current-buffer buffer
diff --git a/tests/git-auto-commit-mode-tests.el b/tests/git-auto-commit-mode-tests.el
index 8e7c291..fd40dce 100644
--- a/tests/git-auto-commit-mode-tests.el
+++ b/tests/git-auto-commit-mode-tests.el
@@ -28,21 +28,41 @@
 (require 'git-auto-commit-mode)
 
 (describe "New files"
-  (it "Should be added to git"
-    (let* ((temp-dir (make-temp-file "gac-" t))
-           (temp-file (expand-file-name "test" temp-dir))
-           (default-directory temp-dir))
-      (unwind-protect
-          (progn
-            (shell-command "git init")
-            (let ((buffer (find-file-noselect temp-file)))
-              (with-current-buffer buffer
-                (git-auto-commit-mode)
-                (insert "test")
-                (save-buffer)))
-            (expect (shell-command-to-string "git log --format=format:%s")
-                    :to-match (rx string-start "test" string-end)))
-        (delete-directory temp-dir t)))))
+  (describe "When ‘gac-automatically-add-new-files’ is t"
+    (it "Should be added to git"
+      (let* ((gac-automatically-add-new-files-p t)
+             (temp-dir (make-temp-file "gac-" t))
+             (temp-file (expand-file-name "test" temp-dir))
+             (default-directory temp-dir))
+        (unwind-protect
+            (progn
+              (shell-command "git init")
+              (let ((buffer (find-file-noselect temp-file)))
+                (with-current-buffer buffer
+                  (git-auto-commit-mode)
+                  (insert "test")
+                  (save-buffer)))
+              (expect (shell-command-to-string "git log --format=format:%s")
+                      :to-match (rx string-start "test" string-end)))
+          (delete-directory temp-dir t)))))
+
+  (describe "When ‘gac-automatically-add-new-files’ is nil"
+    (it "Shouldn’t be added to git"
+      (let* ((gac-automatically-add-new-files-p nil)
+             (temp-dir (make-temp-file "gac-" t))
+             (temp-file (expand-file-name "test" temp-dir))
+             (default-directory temp-dir))
+        (unwind-protect
+            (progn
+              (shell-command "git init")
+              (let ((buffer (find-file-noselect temp-file)))
+                (with-current-buffer buffer
+                  (git-auto-commit-mode)
+                  (insert "test")
+                  (save-buffer)))
+              (expect (shell-command-to-string "git log --format=format:%s")
+                      :not :to-match (rx string-start "test" string-end)))
+          (delete-directory temp-dir t))))))
 
 (provide 'git-auto-commit-mode-tests)
 ;;; git-auto-commit-mode-tests.el ends here