diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3486df5..f97b6ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
 - [#39](https://github.com/bbatsov/adoc-mode/issues/39): Support spaces in the attributes of code blocks.
 - [#41](https://github.com/bbatsov/adoc-mode/issues/41): Fix unconstrained monospace delimiters.
 - [#49](https://github.com/bbatsov/adoc-mode/issues/49): Prevent Flyspell from generating overlays for links and alike.
+- [#52](https://github.com/bbatsov/adoc-mode/issues/52): Prevent auto-fill-mode from breaking one-line titles and alike.
 
 ## 0.7.0 (2023-03-09)
 
diff --git a/adoc-mode.el b/adoc-mode.el
index 613301b..e79532c 100644
--- a/adoc-mode.el
+++ b/adoc-mode.el
@@ -1705,6 +1705,7 @@ text having adoc-reserved set to symbol `block-del'."
   "Creates a keyword for font-lock which highlights one line titles"
   (list
    `(lambda (end) (adoc-kwf-std end ,(adoc-re-one-line-title level) '(0)))
+   '(0 '(face nil adoc-nobreak t) t)
    '(1 '(face adoc-meta-hide-face adoc-reserved block-del) t)
    `(2 ,text-face t)
    '(3  '(face nil adoc-reserved block-del) t)
@@ -1724,7 +1725,7 @@ text having adoc-reserved set to symbol `block-del'."
                (not (equal adoc-enable-two-line-title (length (match-string 2)))))
            (not (text-property-not-all (match-beginning 0) (match-end 0) 'adoc-reserved nil))))
    ;; highlighers
-   `(2 ,text-face t)
+   `(2 '(face ,text-face adoc-nobreak t) t) ;; adoc-nobreak does not hurt here
    `(3 '(face adoc-meta-hide-face adoc-reserved block-del) t)))
 
 ;; (defun adoc-?????-attributes (endpos enddelchar)
@@ -2536,7 +2537,8 @@ Use this function as matching function MATCHER in `font-lock-keywords'."
    (adoc-kw-inline-macro-urls-attribute-list)
    (adoc-kw-inline-macro "anchor" nil nil nil adoc-anchor-face t '("xreflabel"))
    (adoc-kw-inline-macro "xref" nil nil nil '(adoc-reference-face adoc-internal-reference-face) t
-                         '(("caption") (("caption" . adoc-reference-face))))
+                         '(("caption") (("caption" . adoc-reference-face)))
+                         '(adoc-nobreak t)) ;; TODO: Currently, multiline does not work on xref.  So I put adoc-nobreak on the link text at least.  That may hurt on long links texts.
    (adoc-kw-inline-macro "footnote" t nil nil nil nil adoc-secondary-text-face)
    (adoc-kw-inline-macro "footnoteref" t 'single-attribute nil nil nil
                          '(("id") (("id" . adoc-internal-reference-face))))
@@ -3751,7 +3753,7 @@ Turning on Adoc mode runs the normal hook `adoc-mode-hook'."
                 nil nil nil nil
                 (font-lock-multiline . t)
                 (font-lock-mark-block-function . adoc-font-lock-mark-block-function)))
-  (setq-local font-lock-extra-managed-props '(adoc-reserved adoc-attribute-list adoc-code-block adoc-flyspell-ignore))
+  (setq-local font-lock-extra-managed-props '(adoc-reserved adoc-attribute-list adoc-code-block adoc-flyspell-ignore adoc-nobreak))
   (setq-local font-lock-unfontify-region-function 'adoc-unfontify-region-function)
   (setq-local font-lock-extend-after-change-region-function #'adoc-font-lock-extend-after-change-region)
 
@@ -3771,6 +3773,8 @@ Turning on Adoc mode runs the normal hook `adoc-mode-hook'."
   ;; nil, or even something else. See also similar comment in sgml-mode.
   (setq-local imenu-create-index-function 'adoc-imenu-create-index)
 
+  (add-hook 'fill-nobreak-predicate 'adoc-nobreak-p 90 t)
+
   ;; compilation
   (when (boundp 'compilation-error-regexp-alist-alist)
     (add-to-list 'compilation-error-regexp-alist-alist
@@ -3790,7 +3794,7 @@ Turning on Adoc mode runs the normal hook `adoc-mode-hook'."
 (adoc-calc)
 
 
-;; Flyspell
+;; Flyspell and auto-fill
 
 (defun adoc-flyspell-p ()
   "Function for `flyspell-mode-predicate' property of `adoc-mode'.
@@ -3802,6 +3806,11 @@ Returns t if word at point should be checked, nil otherwise."
 
 (put 'adoc-mode 'flyspell-mode-predicate 'adoc-flyspell-p)
 
+(defun adoc-nobreak-p ()
+  "Return t if inserting a newline at point by auto-fill is prohibited."
+  (font-lock-ensure (line-beginning-position) (line-end-position 2)) ;; Must work for two-line-title!
+  (get-text-property (point) 'adoc-nobreak))
+
 (provide 'adoc-mode)
 
 ;; Local Variables: