diff --git a/lens.lisp b/lens.lisp
index 4bbda76..cf8aa7f 100644
--- a/lens.lisp
+++ b/lens.lisp
@@ -115,11 +115,16 @@
     (<= (length it)
         len)))
 
-(defun applicable-when (fun test)
-  (lambda (it)
-    (if (funcall test it)
-        (funcall fun it)
-        it)))
+(defun applicable-when (fun test &optional (default nil default-p))
+  (if default-p
+      (lambda (it)
+        (if (funcall test it)
+            (funcall fun it)
+            default))
+      (lambda (it)
+        (if (funcall test it)
+            (funcall fun it)
+            it))))
 
 (defmacro conj (&rest fns)
   (let ((dat (gensym "dat")))
diff --git a/t/lens.lisp b/t/lens.lisp
index 953dc15..9109590 100644
--- a/t/lens.lisp
+++ b/t/lens.lisp
@@ -84,6 +84,9 @@
   (5am:is (equal 1
                  (funcall (data-lens:applicable-when '1+ (constantly nil))
                           1)))
+  (5am:is (equal "hi"
+                 (funcall (data-lens:applicable-when '1+ (constantly nil) "hi")
+                          1)))
   (5am:is (equal 2
                  (funcall (data-lens:applicable-when '1+ (constantly t))
                           1))))