diff --git a/gc.c b/gc.c
index 66556041..e1137c01 100644
--- a/gc.c
+++ b/gc.c
@@ -1215,6 +1215,9 @@ void gc_thread_data_init(gc_thread_data *thd, int mut_num, char *stack_base, lon
       (1 - STACK_GROWS_DOWNWARD));
     exit(1);
   }
+  thd->stack_traces = calloc(MAX_STACK_TRACES, sizeof(char *));
+  thd->stack_trace_idx = 0;
+  thd->stack_prev_frame = NULL;
   //thd->mutator_num = mut_num;
   thd->jmp_start = malloc(sizeof(jmp_buf));
   thd->gc_args = malloc(sizeof(object) * NUM_GC_ANS);
@@ -1236,10 +1239,18 @@ void gc_thread_data_init(gc_thread_data *thd, int mut_num, char *stack_base, lon
 void gc_thread_data_free(gc_thread_data *thd)
 {
   if (thd) {
+    if (pthread_mutex_destroy(&thd->lock) != 0) {
+      // TODO: can only destroy the lock if it is unlocked. need to make sure we
+      // can guarantee that is the case prior to making this call
+      // On the other hand, can we just use sleep and a loop to retry??
+      fprintf(stderr, "Thread mutex is locked, unable to free\n");
+      exit(1);
+    }
     if (thd->jmp_start) free(thd->jmp_start);
     if (thd->gc_args) free(thd->gc_args);
     if (thd->moveBuf) free(thd->moveBuf);
     if (thd->mark_buffer) free(thd->mark_buffer);
+    if (thd->stack_traces) free(thd->stack_traces);
     free(thd);
   }
 }
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 3d423096..1c375c81 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -31,6 +31,19 @@
 // Size of a "page" on the heap (the second generation), in bytes.
 #define HEAP_SIZE 6000000
 
+// Number of functions to save for printing call history
+#define MAX_STACK_TRACES 10
+
+// GC debugging flags
+#define GC_DEBUG_TRACE 0
+#define GC_DEBUG_VERBOSE 0
+
+/* Additional runtime checking of the GC system.
+   This is here because these checks should not be
+   necessary if GC is working correctly. */
+#define GC_SAFETY_CHECKS 1
+
+
 /* Define general object type. */
 typedef void *object;
 
@@ -186,15 +199,6 @@ gc_heap *gc_get_heap();
 // TODO:
 //void gc_collector()
 
-/* GC debugging flags */
-#define GC_DEBUG_TRACE 0
-#define GC_DEBUG_VERBOSE 0
-
-/* Additional runtime checking of the GC system.
-   This is here because these checks should not be
-   necessary if GC is working correctly. */
-#define GC_SAFETY_CHECKS 1
-
 /* Show diagnostic information for the GC when program terminates */
 #define DEBUG_SHOW_DIAG 0
 
diff --git a/runtime.c b/runtime.c
index 401e96a6..32b4caf4 100644
--- a/runtime.c
+++ b/runtime.c
@@ -188,8 +188,6 @@ static symbol_type Cyc_void_symbol = {{0}, symbol_tag, "", nil};
 const object quote_void = &Cyc_void_symbol;
 
 /* Stack Traces */
-static const int MAX_STACK_TRACES = 10;
-
 void Cyc_st_add(void *data, char *frame) { 
   gc_thread_data *thd = (gc_thread_data *)data;
   // Do not allow recursion to remove older frames
@@ -2479,13 +2477,6 @@ void Cyc_apply_from_buf(void *data, int argc, object prim, object *buf) {
 
 void Cyc_start_thread(gc_thread_data *thd)
 {
-  thd->stack_trace_idx = 0;
-  thd->stack_prev_frame = NULL;
-  // TODO: may need to relocate the calloc to another function that
-  // initializes thread objects, rather than here that just calls them.
-  // at a minimum, should initialize it to NULL so we can test for that here.
-  thd->stack_traces = calloc(MAX_STACK_TRACES, sizeof(char *));
-
   /* Tank, load the jump program... */
   setjmp(*(thd->jmp_start));