diff --git a/bin/pre.slime b/bin/pre.slime
index 7e14df8..3568efa 100644
--- a/bin/pre.slime
+++ b/bin/pre.slime
@@ -46,10 +46,15 @@
   (define (rec clauses)
     (if (= nil clauses)
         nil
-      (list 'if (first (first clauses))
-            (pair 'prog (rest (first clauses)))
-            (rec (rest clauses)))))
-  (rec clauses))
+      (if (= (first (first clauses)) 'else)
+          (prog
+           (if (not (= () (rest clauses)))
+               (error "There are additional clauses after the else clause!")
+             (pair 'prog (rest (first clauses)))))
+        (list 'if (first (first clauses))
+              (pair 'prog (rest (first clauses)))
+              (rec (rest clauses))))))
+    (rec clauses))
 
 (define (nil? x)
   "Checks if the argument is nil."
diff --git a/bin/tests/sicp.slime b/bin/tests/sicp.slime
index 16cf022..8b393f7 100644
--- a/bin/tests/sicp.slime
+++ b/bin/tests/sicp.slime
@@ -1,6 +1,6 @@
 (define (abs x)
   (cond ((< x 0) (- x))
-        (t x)))
+        (else x)))
 
 (assert (= (abs 1) 1))
 (assert (= (abs (- 2)) 2))
@@ -151,7 +151,7 @@
 (define (A m n)
     (cond ((= m 0) (+ n 1))
           ((= n 0) (A (- m 1) 1))
-          (t (A (- m 1) (A m (- n 1))))))
+          (else (A (- m 1) (A m (- n 1))))))
 
 (assert (= (A 0 0) 1))
 (assert (= (A 1 2) 4))
@@ -165,7 +165,7 @@
 (define (fib n)
   (cond ((= n 0) 0)
         ((= n 1) 1)
-        (t (+ (fib (- n 1)) (fib (- n 2))))))
+        (else (+ (fib (- n 1)) (fib (- n 2))))))
 
 (define (fib2 n)
   (fib-iter 1 0 n))
@@ -195,7 +195,7 @@
 ;;   (define (cc amount kinds-of-coins)
 ;;     (cond ((= amount 0) 1)
 ;;           ((or (< amount 0) (= kinds-of-coins 0)) 0)
-;;           (t (+ (cc amount (- kinds-of-coins 1))
+;;           (else (+ (cc amount (- kinds-of-coins 1))
 ;;                 (cc (- amount (first-denomination kinds-of-coins)) kinds-of-coins)))))
 
 ;;   (define (first-denomination kinds-of-coins)
@@ -232,7 +232,7 @@
 
   (cond ((= n 0) 1)
         ((even? n) (square (fast-expt b (/ n 2))))
-        (t (* b (fast-expt b (- n 1))))))
+        (else (* b (fast-expt b (- n 1))))))
 
 (assert (= (expt 1 2) 1))
 (assert (= (expt 2 2) 4))
@@ -269,7 +269,7 @@
 (define (find-divisor n test-divisor)
   (cond ((> (square test-divisor) n) n)
         ((divides? test-divisor n) test-divisor)
-        (t (find-divisor n (+ test-divisor 1)))))
+        (else (find-divisor n (+ test-divisor 1)))))
 
 (define (divides? a b)
   (= (% b a) 0))
@@ -333,7 +333,7 @@
       (let ((test-value (f midpoint)))
         (cond ((positive? test-value) (search f neg-point midpoint))
               ((negative? test-value) (search f midpoint pos-point))
-              (t midpoint))))))
+              (else midpoint))))))
 
 (define (close-enough? x y) (< (abs (- x y)) 0.001))