diff --git a/gc.c b/gc.c
index 1f9ccebe..fe6a8d75 100644
--- a/gc.c
+++ b/gc.c
@@ -675,6 +675,9 @@ void gc_thread_data_init(gc_thread_data *thd, char *stack_base, long stack_size)
       (1 - STACK_GROWS_DOWNWARD));
     exit(1);
   }
+  thd->jmp_start = malloc(sizeof(jmp_buf));
+  thd->gc_ans = malloc(sizeof(object) * NUM_GC_ANS);
+  thd->gc_num_ans = 0;
   thd->moveBufLen = 0;
   gc_thr_grow_move_buffer(thd);
 // TODO: depends on collector state:  thd->gc_alloc_color = ATOMIC_GET(&gc_;
@@ -692,6 +695,8 @@ void gc_thread_data_init(gc_thread_data *thd, char *stack_base, long stack_size)
 void gc_thread_data_free(gc_thread_data *thd)
 {
   if (thd) {
+    if (thd->jmp_start) free(thd->jmp_start);
+    if (thd->gc_ans) free(thd->gc_ans);
     if (thd->moveBuf) free(thd->moveBuf);
     if (thd->mark_buffer) free(thd->mark_buffer);
     free(thd);
diff --git a/include/cyclone/runtime-main.h b/include/cyclone/runtime-main.h
index a68c721b..0bc2cc76 100644
--- a/include/cyclone/runtime-main.h
+++ b/include/cyclone/runtime-main.h
@@ -60,7 +60,7 @@ static void Cyc_main (stack_size,heap_size,stack_base)
   start = clock(); /* Start the timing clock. */
 
   /* Tank, load the jump program... */
-  setjmp(jmp_main);
+  setjmp(*(Cyc_thread->jmp_start));
 #if DEBUG_GC
   printf("Done with GC\n");
 #endif
diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 63b98f1b..c1568c6b 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -225,7 +225,6 @@ extern long no_major_gcs; /* Count the number of GC's. */
 extern object gc_cont;   /* GC continuation closure. */
 extern object gc_ans[NUM_GC_ANS];    /* argument for GC continuation closure. */
 extern int gc_num_ans;
-extern jmp_buf jmp_main; /* Where to jump to. */
 
 /* Define Lisp constants we need. */
 extern const object boolean_t;
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 54e30236..fe8522a7 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -28,7 +28,7 @@
 // This is used as the first generation of the GC.
 #define STACK_SIZE 250000
 
-// Size of a "page" on the heap (the 2nd generation), in bytes.
+// Size of a "page" on the heap (the second generation), in bytes.
 #define HEAP_SIZE 6000000
 
 /* Define general object type. */
@@ -40,7 +40,7 @@ struct gc_thread_data_t {
   // Data needed for stack-based minor GC
   char *stack_start;
   char *stack_limit;
-TODO:
+  jmp_buf *jmp_start;
   object gc_cont;
   object *gc_ans; //[NUM_GC_ANS];
   short gc_num_ans;
diff --git a/runtime.c b/runtime.c
index 3527a3a4..25a55c89 100644
--- a/runtime.c
+++ b/runtime.c
@@ -82,7 +82,7 @@ void Cyc_check_bounds(void *data, const char *label, int len, int index) {
 gc_heap *Cyc_heap;
 gc_thread_data *Cyc_thread;
 
-TODO: get rid of globals below that are not needed
+//TODO: get rid of globals below that are not needed
 clock_t start;   /* Starting time. */
 char *bottom;    /* Bottom of tospace. */
 char *allocp;    /* Cheney allocate pointer. */
@@ -98,11 +98,10 @@ char *dhalloc_end;
 long no_gcs = 0; /* Count the number of GC's. */
 long no_major_gcs = 0; /* Count the number of GC's. */
 
-TODO: after previous change, move these to thread data structure
+//TODO: after previous change, move these to thread data structure
 object gc_cont;   /* GC continuation closure. */
 object gc_ans[NUM_GC_ANS];    /* argument for GC continuation closure. */
 int gc_num_ans;
-jmp_buf jmp_main; /* Where to jump to. */
 
 object Cyc_global_variables = nil;
 int _cyc_argc = 0;
@@ -2746,7 +2745,12 @@ void GC(void *data, closure cont, object *args, int num_args)
   }
 
   /* Let it all go, Neo... */
-  longjmp(jmp_main, (int)(&data)); // Return globals gc_cont, gc_ans
+  // TODO: apparently it is a bad idea to cast a pointer to an int on 64 bit platforms
+  // as a pointer may be larger than an int. so need to figure out another technique
+  // here to communicate back to the setjmp which data to use. need to store a data
+  // structure of thread buffers for heap gc, so maybe be able to use an int to index
+  // into that.
+  longjmp(*(((gc_thread_data *)data)->jmp_start), (int)(&data)); // Return globals gc_cont, gc_ans
 }