diff --git a/runtime.c b/runtime.c
index 4f7c97d6..ab60d34b 100644
--- a/runtime.c
+++ b/runtime.c
@@ -880,13 +880,13 @@ object memqp(void *data, object x, list l)
  */
 object equalp(object x, object y)
 {
-  object slow_lis = x, fast_lis;
+  object slow_lis = x, fast_lis = NULL;
   int second_cycle = 0;
 
-//  if (Cyc_is_pair(x) == boolean_t &&
-//      Cyc_is_pair(cdr(x)) == boolean_t){
-//    fast_lis = cdr(x);
-//  }
+  if (Cyc_is_pair(x) == boolean_t &&
+      Cyc_is_pair(cdr(x)) == boolean_t){
+    fast_lis = cdr(x);
+  }
 
   for (;; x = cdr(x), y = cdr(y)) {
     if (equal(x, y))
@@ -900,30 +900,31 @@ object equalp(object x, object y)
     if (boolean_f == equalp(car(x), car(y)))
       return boolean_f;
 
-//    // If there is no cycle, keep checking equality
-//    if (fast_lis == NULL ||
-//        Cyc_is_pair(fast_lis) == boolean_f ||
-//        cdr(fast_lis) == NULL ||
-//        Cyc_is_pair(cdr(fast_lis)) == boolean_f ||
-//        cddr(fast_lis) == NULL){
-//      continue;
-//    }
-//
-//    // If there is a cycle, handle it
-//    if (slow_lis == fast_lis) {
-//      // if this is y, both lists have cycles and are equal, return #t
-//      if (second_cycle)
-//        return boolean_t;
-//      // if this is x, keep going and check for a cycle in y
-//      second_cycle = 1;
-//      slow_lis = y;
-//      if (Cyc_is_pair(y) == boolean_t) {
-//        fast_lis = cdr(y);
-//      }
-//      continue;
-//    }
-//    slow_lis = cdr(slow_lis);
-//    fast_lis = cddr(fast_lis);
+    // If there is no cycle, keep checking equality
+    if (fast_lis == NULL ||
+        Cyc_is_pair(fast_lis) == boolean_f ||
+        cdr(fast_lis) == NULL ||
+        Cyc_is_pair(cdr(fast_lis)) == boolean_f ||
+        cddr(fast_lis) == NULL){
+      continue;
+    }
+
+    // If there is a cycle, handle it
+    if (slow_lis == fast_lis) {
+      // if this is y, both lists have cycles and are equal, return #t
+      if (second_cycle)
+        return boolean_t;
+      // if this is x, keep going and check for a cycle in y
+      second_cycle = 1;
+      slow_lis = y;
+      fast_lis = NULL;
+      if (Cyc_is_pair(y) == boolean_t) {
+        fast_lis = cdr(y);
+      }
+      continue;
+    }
+    slow_lis = cdr(slow_lis);
+    fast_lis = cddr(fast_lis);
   }
 }