diff --git a/src/beowulf/eval.clj b/src/beowulf/eval.clj
index ab1be39..2604ade 100644
--- a/src/beowulf/eval.clj
+++ b/src/beowulf/eval.clj
@@ -198,7 +198,7 @@
   See page 12 of the Lisp 1.5 Programmers Manual."
   [a y]
   (cond
-    (primitive-atom? y) (sub2 a y)
+    (= (primitive-atom? y) 'T) (sub2 a y)
     :else
     (make-cons-cell (sublis a (car y)) (sublis a (cdr y)))))
 
diff --git a/test/beowulf/bootstrap_test.clj b/test/beowulf/bootstrap_test.clj
index 7ac3936..6813ccc 100644
--- a/test/beowulf/bootstrap_test.clj
+++ b/test/beowulf/bootstrap_test.clj
@@ -218,3 +218,12 @@
                      'D
                      (gsp "((A . (M N)) (B . (CAR X)) (C . (QUOTE M)) (C . (CDR X)))")))]
       (is (= actual expected)))))
+
+(deftest sublis-tests
+  (testing "sublis"
+    (let [expected "(SHAKESPEARE WROTE (THE TEMPEST))"
+          actual (print-str
+                   (sublis
+                     (gsp "((X . SHAKESPEARE) (Y . (THE TEMPEST)))")
+                     (gsp "(X WROTE Y)")))]
+      (is (= actual expected)))))