diff --git a/notes.org b/notes.org
index f7f2d75..7f834e0 100644
--- a/notes.org
+++ b/notes.org
@@ -430,6 +430,32 @@ Not sure if clearing the cache is necessary here, because it seemed to make near
                                            :action '(org-get-heading t t))))))
 #+END_SRC
 
+*** =deadline=
+
+#+BEGIN_SRC elisp
+  (org-ql-preamble-bench :times 1
+                         :file "~/org/inbox.org"
+                         :query (deadline))
+#+END_SRC
+
+#+RESULTS:
+| Form                    | x faster than next | Total runtime | # of GCs | Total GC runtime |
+|-------------------------+--------------------+---------------+----------+------------------|
+| preamble: (deadline)    | 27.63              |      0.014656 |        0 |                0 |
+| no preamble: (deadline) | slowest            |      0.404952 |        0 |                0 |
+
+#+BEGIN_SRC elisp
+  (org-ql-preamble-bench :times 1
+                         :file "~/org/inbox.org"
+                         :query (deadline <= "2019-01-01"))
+#+END_SRC
+
+#+RESULTS:
+| Form                                    | x faster than next | Total runtime | # of GCs | Total GC runtime |
+|-----------------------------------------+--------------------+---------------+----------+------------------|
+| preamble: (deadline <= "2019-01-01")    | 27.91              |      0.014606 |        0 |                0 |
+| no preamble: (deadline <= "2019-01-01") | slowest            |      0.407682 |        0 |                0 |
+
 *** =level=
 
 #+BEGIN_SRC elisp
diff --git a/org-ql.el b/org-ql.el
index 58a3286..0a9f431 100644
--- a/org-ql.el
+++ b/org-ql.el
@@ -316,6 +316,15 @@ replace the clause with a preamble."
                                 element)
                               (pcase element
                                 (`(or _) element)
+                                (`(deadline . ,_)
+                                 (setq org-ql-preamble
+                                       (rx-to-string `(seq bol (0+ (any "	 ")) "DEADLINE" ":" (1+ space) (1+ not-newline)) t))
+                                 ;; Return element, because the predicate still needs testing.
+                                 element)
+                                (`(deadline)
+                                 (setq org-ql-preamble (rx-to-string `(seq bol (0+ (any "	 ")) "DEADLINE" ":") t))
+                                 ;; Return element, because the predicate still needs testing.
+                                 element)
                                 (`(regexp . ,regexps)
                                  (setq org-ql-preamble (rx-to-string `(or ,@regexps) t))
                                  ;; Return nil, because we don't need to test the predicate.