diff --git a/collects/mzlib/kw.rkt b/collects/mzlib/kw.rkt
index 6645627..014f596 100644
--- a/collects/mzlib/kw.rkt
+++ b/collects/mzlib/kw.rkt
@@ -128,7 +128,7 @@
        [else (ormap (lambda (k) (and (assq k rests) #t)) ; suggested?
                     (car (cddddr processed-spec)))])))
   (define (make-keyword-get-expr key rest default known-vars)
-    ;; expand (for id macros) and check if its a simple expression, because if
+    ;; expand (for id macros) and check if it's a simple expression, because if
     ;; it is, evaluation cannot have side-effects and we can use keyword-get*
     (define default*
       (local-expand default 'expression (cons #'#%app known-vars)))
diff --git a/collects/mzlib/thread.rkt b/collects/mzlib/thread.rkt
index 4c4d005..c4bcf7a 100644
--- a/collects/mzlib/thread.rkt
+++ b/collects/mzlib/thread.rkt
@@ -7,7 +7,7 @@
 
   #|
   t accepts a function, f, and creates a thread. It returns the thread and a
-  function, g. When g is applied it passes it's argument to f, and evaluates
+  function, g. When g is applied it passes its argument to f, and evaluates
   the call of f in the time of the thread that was created. Calls to g do not
   block.
   |#