diff --git a/words/main.rkt b/words/main.rkt
index 76b71d2..29cd069 100644
--- a/words/main.rkt
+++ b/words/main.rkt
@@ -4,6 +4,7 @@
 
 (define (make-words #:letters [letters "etaoinshrdluw"]
                     #:mandatory [mandatory #f]
+                    #:combo [combo #f]
                     #:min [min-length 5]
                     #:max [max-length 10]
                     #:hide-plurals [hide-plurals? #t]
@@ -12,39 +13,43 @@
                     #:all-caps [all-caps? #f]
                     #:initial-caps [initial-caps? #f])
   (define mandatory-cs
-    (if mandatory (remove-duplicates (for/list ([c (in-string mandatory)])
-                                       (char-downcase c)) char=?) null))
+    (if (or mandatory combo)
+        (remove-duplicates
+         (for/list ([c (in-string (string-append (or mandatory "") (or combo "")))])
+                   (char-downcase c)) char=?) null))
   (define letter-cs-charidx
     (word->charidx
      (list->string
       (remove-duplicates
        (append (if letters
                    (for/list ([c (in-string letters)])
-                     (char-downcase c))
+                             (char-downcase c))
                    null)
                mandatory-cs)
        char=?))))
   (define caser (cond
-                 [all-caps? string-upcase]
-                 [initial-caps? string-titlecase]
-                 [else values]))
+                  [all-caps? string-upcase]
+                  [initial-caps? string-titlecase]
+                  [else values]))
   (for*/fold ([word-acc null]
               [count 0]
               #:result word-acc)
              ([idx (in-list (shuffle (range (vector-length wordrecs))))]
               [rec (in-value (vector-ref wordrecs idx))]
               [word-charidx (in-value (word-rec-charint rec))]
+              [word (in-value (word-rec-word rec))]
               #:break (= count (or max-words +inf.0))
               #:when (and
                       ;; between min and max length
                       ((if (<= min-length max-length) <= >=) min-length (word-rec-length rec) max-length)
                       ;; word contains each mandatory char, case-insensitive
-                      (or (not mandatory)
-                          (for/and ([mc (in-list mandatory-cs)])
-                            (word-charidx . contains-char? . mc)))
+                      (for/and ([mc (in-list mandatory-cs)])
+                               (word-charidx . contains-char? . mc))
                       ;; word contains only letters + mandatory, case-insensitive
                       (for/and ([wc (in-list (map char-downcase (charidx->chars word-charidx)))])
-                        (letter-cs-charidx . contains-char? . wc))
+                               (letter-cs-charidx . contains-char? . wc))
+                      (or (not combo)
+                          (regexp-match combo word))
                       ;; maybe only proper names
                       (if proper-names?
                           (capitalized? word-charidx)
@@ -52,10 +57,10 @@
                       ;; maybe hide plurals
                       (or (not hide-plurals?)
                           (not (word-rec-plural? rec)))))
-    (values (cons (caser (word-rec-word rec)) word-acc) (add1 count))))
+    (values (cons (caser word) word-acc) (add1 count))))
 
 (module+ test
   (require rackunit)
   (time (make-words))
-  (check-equal? (sort (make-words #:mandatory "xyz") string<?)
-                '("azoxy" "dysoxidize" "isazoxy" "oxytonize" "rhizotaxy" "zootaxy")))
\ No newline at end of file
+  (check-equal? (sort (make-words #:mandatory "xyz" #:combo #false) string<?)
+                  '("azoxy" "dysoxidize" "isazoxy" "oxytonize" "rhizotaxy" "zootaxy")))
\ No newline at end of file